In the year 380 the emperors Gratian and Theodosius I decided to convoke this council to counter the Arians, and also to judge the case of Maximus the Cynic, bishop of Constantinople. The council met in May of the following year. One hundred and fifty bishops took part, all of them eastern Orthodox, since the Pneumatomachi party had left at the start.
After Maximus had been condemned, Meletius, bishop of Antioch, appointed Gregory of Nazianzus as the lawful bishop of Constantinople and at first presided over the council. Then on Meletius' sudden death, Gregory took charge of the council up to the arrival of Acholius, who was to table Pope Damasus' demands: namely, that Maximus should be expelled as an interloper, and that the translation of bishops should be avoided. But when Timothy, bishop of Alexandria, arrived he declared Gregory's appointment invalid. Gregory resigned the episcopacy and Nectarius, after baptism and consecration, was installed as bishop and presided over the council until its closure.
No copy of the council's doctrinal decisions, entitled tomos kai anathematismos engraphos (record of the tome and anathemas), has survived. So what is presented here is the synodical letter of the synod of Constantinople held in 382, which expounded these doctrinal decisions, as the fathers witness, in summary form: namely, along the lines defined by the council of Nicaea, the consubstantiality and co-eternity of the three divine persons against the Sabellians, Anomoeans, Arians and Pneumatomachi, who thought that the divinity was divided into several natures; and the enanthropesis (taking of humanity) of the Word, against those who supposed that the Word had in no way taken a human soul. All these matters were in close agreement with the tome that Pope Damasus and a Roman council, held probably in 378, had sent to the East.
Scholars find difficulties with the creed attributed to the council of Constantinople. Some say that the council composed a new creed. But no mention is made of this creed by ancient witnesses until the council of Chalcedon; and the council of Constantinople was said simply to have endorsed the faith of Nicaea, with a few additions on the holy Spirit to refute the Pneumatomachian heresy. Moreover, if the latter tradition is accepted, an explanation must be given of why the first two articles of the so-called Constantinopolitan creed differ considerably from the Nicene creed.
It was J. Lebon, followed by J. N. D. Kelly and A. M. Ritter, who worked at the solution of this problem. Lebon said that the Nicene creed, especially since it was adapted to use at baptism, had taken on a number of forms. It was one of these which was endorsed at the council of Constantinople and developed by additions concerning the holy Spirit. All the forms, altered to some extent or other, were described by a common title as "the Nicene faith". Then the council of Chalcedon mentioned the council of Constantinople as the immediate source of one of them, marked it out by a special name "the faith of the 150 fathers", which from that time onwards became its widely known title, and quoted it alongside the original simple form of the Nicene creed. The Greek text of the Constantinopolitan creed, which is printed below, is taken from the acts of the council of Chalcedon.
The council of Constantinople enacted four disciplinary canons: against the Arian heresy and its sects (can. 1), on limiting the power of bishops within fixed boundaries (can. 2), on ranking the see of Constantinople second to Rome in honour and dignity (can. 3), on the condemnation of Maximus and his followers (can. 4). Canons 2-4 were intended to put a stop to aggrandisement on the part of the see of Alexandria. The two following canons, 5 and 6, were framed at the synod which met in Constantinople in 382. The 7th canon is an extract from a letter which the church of Constantinople sent to Martyrius of Antioch.
The council ended on 9 July 381, and on 30 July of the same year, at the request of the council fathers, the emperor Theodosius ratified its decrees by edict .
Already from 382 onwards, in the synodical letter of the synod which met at Constantinople, the council of Constantinople was given the title of "ecumenical". The word denotes a general and plenary council. But the council of Constantinople was criticised and censured by Gregory of Nazianzus. In subsequent years it was hardly ever mentioned. In the end it achieved its special status when the council of Chalcedon, at its second session and in its definition of the faith, linked the form of the creed read out at Constantinople with the Nicene form, as being a completely reliable witness of the authentic faith. The fathers of Chalcedon acknowledged the authority of the canons — at least as far as the eastern church was concerned — at their sixteenth session. The council's dogmatic authority in the western church was made clear by words of Pope Gregory I: "I confess that I accept and venerate the four councils (Nicaea, Constantinople, Ephesus and Chalcedon) in the same way as I do the four books of the holy Gospel...."
The bishop of Rome's approval was not extended to the canons, because they were never brought "to the knowledge of the apostolic see''. Dionysius Exiguus knew only of the first four — the ones to be found in the western collections. Pope Nicholas I wrote of the sixth canon to Emperor Michael III: "It is not found among us, but is said to be in force among you''.
The English translation is from the Greek text, which is the more authoritative version.
The Exposition Of The 150 Fathers
We believe in one God the Father all-powerful, maker of heaven and of earth, and of all things both seen and unseen. And in one Lord Jesus Christ, the only-begotten Son of God, begotten from the Father before all the ages, light from light, true God from true God, begotten not made, consubstantial with the Father, through whom all things came to be; for us humans and for our salvation he came down from the heavens and became incarnate from the holy Spirit and the virgin Mary, became human and was crucified on our behalf under Pontius Pilate; he suffered and was buried and rose up on the third day in accordance with the scriptures; and he went up into the heavens and is seated at the Father's right hand; he is coming again with glory to judge the living and the dead; his kingdom will have no end. And in the Spirit, the holy, the lordly and life-giving one, proceeding forth from the Father, co-worshipped and co-glorified with Father and Son, the one who spoke through the prophets; in one, holy, catholic and apostolic church. We confess one baptism for the forgiving of sins. We look forward to a resurrection of the dead and life in the age to come. Amen.
A Letter Of The Bishops Gathered In Constantinople 
To the most honoured lords and most reverend brethren and fellow-ministers, Damasus, Ambrose, Britton, Valerian, Acholius, Anemius, Basil, and the rest of the holy bishops who met in the great city of Rome: the sacred synod of orthodox bishops who met in the great city of Constantinople sends greetings in the Lord.
It may well be unnecessary to instruct your reverence by describing the many sufferings that have been brought upon us under Arian domination, as if you did not know already. Nor do we imagine that your piety considers our affairs so trivial that you need to learn what you must be suffering along with us. Nor were the storms which beset us such as to escape your notice on grounds of insignificance. The period of persecution is still recent and ensures that the memory remains fresh not only among those who have suffered but also among those who have through love made the lot of those who suffered their own. It was barely yesterday or the day before that some were freed from the bonds of exile and returned to their own churches through a thousand tribulations. The remains of others who died in exile were brought back. Even after their return from exile some experienced a ferment of hatred from the heretics and underwent a more cruel fate in their own land than they did abroad, by being stoned to death by them in the manner of the blessed Stephen. Others were torn to shreds by various tortures and still carry around on their bodies the marks of Christ's wounds and bruises. Who could number the financial penalties, the fines imposed on cities, the confiscations of individual property, the plots, the outrages, the imprisonments? Indeed all our afflictions increased beyond number: perhaps because we were paying the just penalty for our sins; perhaps also because a loving God was disciplining us by means of the great number of our sufferings.
So thanks be to God for this. He has instructed his own servants through the weight of their afflictions, and in accordance with his numerous mercies he has brought us back again to a place of refreshment The restoration of the churches demanded prolonged attention, much time and hard work from us if the body of the church which had been weak for so long was to be cured completely by gradual treatment and brought back to its original soundness in religion. We may seem on the whole to be free from violent persecutions and to be at the moment recovering the churches which have long been in the grip of the heretics. But in fact we are oppressed by wolves who even after expulsion from the fold go on ravaging the flocks up and down dale, making so bold as to hold rival assemblies, activating popular uprisings and stopping at nothing which might harm the churches. As we have said, this made us take a longer time over our affairs.
But now you have shown your brotherly love for us by convoking a synod in Rome, in accordance with God's will, and inviting us to it, by means of a letter from your most God-beloved emperor, as if we were limbs of your very own, so that whereas in the past we were condemned to suffer alone, you should not now reign in isolation from us, given the complete agreement of the emperors in matters of religion. Rather, according to the word of the apostle, we should reign along with you'. So it was our intention that if it were possible we should all leave our churches together and indulge our desires rather than attend to their needs. But who will give us wings as of a dove, so we shall fly and come to rest with you? This course would leave the churches entirely exposed, just as they are beginning their renewal; and it is completely out of the question for the majority. As a consequence of last year's letter sent by your reverence after the synod of Aquileia to our most God-beloved emperor Theodosius, we came together in Constantinople. We were equipped only for this stay in Constantinople and the bishops who remained in the provinces gave their agreement to this synod alone. We foresaw no need for a longer absence, nor did we hear of it in advance at all, before we gathered in Constantinople. On top of this the tightness of the schedule proposed allowed no opportunity to prepare for a longer absence, nor to brief all the bishops in the provinces who are in communion with us and to get their agreement. Since these considerations, and many more besides, prevented most of us from coming, we have done the next best thing both to set matters straight and to make your love for us appreciated: we have managed to convince our most venerable and reverend brethren and fellow-ministers, Bishops Cyriacus, Eusebius and Priscian to be willing to undertake the wearisome journey to you. Through them we wish to show that our intentions are peaceful and have unity as their goal. We also want to make clear that what we are zealously seeking is sound faith.
What we have undergone — persecutions, afflictions, imperial threats, cruelty from officials, and whatever other trial at the hands of heretics — we have put up with for the sake of the gospel faith established by the 318 fathers at Nicaea in Bithynia. You, we and all who are not bent on subverting the word of the true faith should give this creed our approval. It is the most ancient and is consistent with our baptism. It tells us how to believe in the name of the Father and of the Son and of the holy Spirit: believing also, of course, that the Father, the Son and the holy Spirit have a single Godhead and power and substance, a dignity deserving the same honour and a co-eternal sovereignty, in three most perfect hypostases, or three perfect persons. So there is no place for Sabellius's diseased theory in which the hypostases are confused and thus their proper characteristics destroyed. Nor may the blasphemy of Eunomians and Arians and Pneumatomachi prevail, with its division of substance or of nature or of Godhead, and its introduction of some nature which was produced subsequently, or was created, or was of a different substance, into the uncreated and consubstantial and co-eternal Trinity. And we preserve undistorted the accounts of the Lord's taking of humanity, accepting as we do that the economy of his flesh was not soulless nor mindless nor imperfect. To sum up, we know that he was before the ages fully God the Word, and that in the last days he became fully man for the sake of our salvation.
So much, in summary, for the faith which is openly preached by us. You can take even more heart concerning these matters if you think fit to consult the tome that was issued in Antioch by the synod which met there as well as the one issued last year in Constantinople by the ecumenical synod. In these documents we confessed the faith in broader terms and we have issued a written condemnation of the heresies which have recently erupted.
With regard to particular forms of administration in the churches, ancient custom, as you know, has been in force, along with the regulation of the saintly fathers at Nicaea, that in each province those of the province, and with them-should the former so desire — their neighbours, should conduct ordinations as need might arise. Accordingly, as you are aware, the rest of the churches are administered, and the priests [= bishops] of the most prominent churches have been appointed, by us. Hence at the ecumenical council by common agreement and in the presence of the most God-beloved emperor Theodosius and all the clergy, and with the approval of the whole city, we have ordained the most venerable and God-beloved Nectarius as bishop of the church newly set up, as one might say, in Constantinople — a church which by God's mercy we just recently snatched from the blasphemy of the heretics as from the lion's jaws. Over the most ancient and truly apostolic church at Antioch in Syria, where first the precious name of "Christians" came into use, the provincial bishops and those of the diocese of the East came together and canonically ordained the most venerable and God-beloved Flavian as bishop with the consent of the whole church, as though it would give the man due honour with a single voice. The synod as a whole also accepted that this ordination was legal. We wish to inform you that the most venerable and God-beloved Cyril is bishop of the church in Jerusalem, the mother of all the churches. He was canonically ordained some time ago by those of the province and at various times he has valiantly combated the Arians.
We exhort your reverence to join us in rejoicing at what we have legally and canonically enacted. Let spiritual love link us together, and let the fear of the Lord suppress all human prejudice and put the building up of the churches before individual attachment or favour. In this way, with the account of the faith agreed between us and with Christian love established among us, we shall cease to declare what was condemned by the apostles, "I belong to Paul, I to Apollo, I to Cephas"; but we shall all be seen to belong to Christ, who has not been divided up among us; and with God's good favour, we shall keep the body of the church undivided, and shall come before the judgment-seat of the Lord with confidence.
The profession of faith of the holy fathers who gathered in Nicaea in Bithynia is not to be abrogated, but it is to remain in force. Every heresy is to be anathematised and in particular that of the Eunomians or Anomoeans, that of the Arians or Eudoxians, that of the Semi-Arians or Pneumatomachi, that of the Sabellians that of the Marcellians, that of the Photinians and that of the Apollinarians.
Diocesan bishops are not to intrude in churches beyond their own boundaries nor are they to confuse the churches: but in accordance with the canons, the bishop of Alexandria is to administer affairs in Egypt only; the bishops of the East are to manage the East alone (whilst safeguarding the privileges granted to the church of the Antiochenes in the Nicene canons); and the bishops of the Asian diocese are to manage only Asian affairs; and those in Pontus only the affairs of Pontus; and those in Thrace only Thracian affairs. Unless invited bishops are not to go outside their diocese to perform an ordination or any other ecclesiastical business. If the letter of the canon about dioceses is kept, it is clear that the provincial synod will manage affairs in each province, as was decreed at Nicaea. But the churches of God among barbarian peoples must be administered in accordance with the custom in force at the time of the fathers.
Because it is new Rome, the bishop of Constantinople is to enjoy the privileges of honour after the bishop of Rome.
Regarding Maximus the Cynic and the disorder which surrounded him in Constantinople: he never became, nor is he, a bishop; nor are those ordained by him clerics of any rank whatsoever. Everything that was done both to him and by him is to be held invalid.
Regarding the Tome  of the Westerns: we have also recognised those in Antioch who confess a single Godhead of Father and Son and holy Spirit.
There are many who are bent on confusing and overturning the good order of the church and so fabricate, out of hatred and a wish to slander, certain accusations against orthodox bishops in charge of churches. Their intention is none other than to blacken priests' reputations and to stir up trouble among peace-loving laity. For this reason the sacred synod of bishops assembled at Constantinople has decided not to admit accusers without prior examination, and not to allow everyone to bring accusations against church administrators — but without excluding everyone. So if someone brings a private (that is a personal) complaint against the bishop on the grounds that he has been defrauded or in some other way unjustly dealt with by him, in the case of this kind of accusation neither the character nor the religion of the accuser will be subject to examination. It is wholly essential both that the bishop should have a clear conscience and that the one who alleges that he has been wronged, whatever his religion may be, should get justice.
But if the charge brought against the bishop is of an ecclesiastical kind, then the characters of those making it should be examined, in the first place to stop heretics bringing charges against orthodox bishops in matters of an ecclesiastical kind. (We define "heretics" as those who have been previously banned from the church and also those later anathematised by ourselves: and in addition those who claim to confess a faith that is sound, but who have seceded and hold assemblies in rivalry with the bishops who are in communion with us.) In the second place, persons previously condemned and expelled from the church for whatever reason, or those excommunicated either from the clerical or lay rank, are not to be permitted to accuse a bishop until they have first purged their own crime. Similarly, those who are already accused are not permitted to accuse a bishop or other clerics until they have proved their own innocence of the crimes with which they are charged. But if persons who are neither heretics nor excommunicates, nor such as have been previously condemned or accused of some transgression or other, claim that they have some ecclesiastical charge to make against the bishop, the sacred synod commands that such persons should first lay the accusations before all the bishops of the province and prove before them the crimes committed by the bishop in the case. If it emerges that the bishops of the province are not able to correct the crimes laid at the bishop's door, then a higher synod of the bishops of that diocese, convoked to hear this case, must be approached, and the accusers are not to lay their accusations before it until they have given a written promise to submit to equal penalties should they be found guilty of making false accusations against the accused bishop, when the matter is investigated.
If anyone shows contempt of the prescriptions regarding the above matters and presumes to bother either the ears of the emperor or the courts of the secular authorities, or to dishonour all the diocesan bishops and trouble an ecumenical synod, there is to be no question whatever of allowing such a person to bring accusations forward, because he has made a mockery of the canons and violated the good order of the church.
Those who embrace orthodoxy and join the number of those who are being saved from the heretics, we receive in the following regular and customary manner: Arians, Macedonians, Sabbatians, Novatians, those who call themselves Cathars and Aristae, Quartodeciman or Tetradites, Apollinarians—these we receive when they hand in statements and anathematise every heresy which is not of the same mind as the holy, catholic and apostolic church of God. They are first sealed or anointed with holy chrism on the forehead, eyes, nostrils, mouth and ears. As we seal them we say: "Seal of the gift of the holy Spirit". But Eunomians, who are baptised in a single immersion, Montanists (called Phrygians here), Sabellians, who teach the identity of Father and Son and make certain other difficulties, and all other sects — since there are many here, not least those who originate in the country of the Galatians — we receive all who wish to leave them and embrace orthodoxy as we do Greeks. On the first day we make Christians of them, on the second catechumens, on the third we exorcise them by breathing three times into their faces and their ears, and thus we catechise them and make them spend time in the church and listen to the scriptures; and then we baptise them.
1. Namely the synod of Constantinople in 382
2. This tome has not survived; it probably defended Paul of Antioch