From the commencement of his reign Innocent III had purposed to assemble an ecumenical council, but only towards the end of his pontificate could he realize this project, by the Bull of 19 April, 1213. The assembly was to take place in November, 1215. The council did in fact meet on 11 November, and its sessions were prolonged until the end of the month. The long interval between the convocation and the opening of the council as well as the prestige of the reigning pontiff, were responsible for the very large number of bishops who attended it, it is commonly cited in canon law as "the General Council of Lateran", without further qualification, or again, as "the Great Council". Innocent III found himself on this occasion surrounded by seventy-one patriarchs and metropolitans, including the Patriarchs of Constantinople and of Jerusalem four hundred and twelve bishops, and nine hundred abbots and priors. The Patriarchs of Antioch and Alexandria were represented by delegates. Envoys appeared from Emperor Frederick II, from Henry Latin Emperor of Constantinople, from the Kings of France, England, Aragon, Hungary, Cyprus, and Jerusalem, and from other princes. The pope himself opened the council with an allocution the lofty views of which surpassed the orator's power of expression. He had desired, said the pope, to celebrate this Pasch before he died. He declared himself ready to drink the chalice of the Passion for the defence of the Catholic Faith, for the succour of the Holy Land, and to establish the liberty of the Church. After this discourse, followed by moral exhortation, the pope presented to the council seventy decrees or canons, already formulated, on the most important points of dogmatic and moral theology. Dogmas were defined points of discipline were decided, measures were drawn up against heretics, and, finally, the conditions of the next crusade were regulated.

The fathers of the council did little more than approve the seventy decrees presented to them; this approbation, nevertheless, sufficed to impart to the acts thus formulated and promulgated the value of {ecumenical decrees. Most of them are somewhat lengthy and are divided into chapters. The following are the most important:

• Canon 1: Exposition of the Catholic Faith and of the dogma of Transubstantiation.
• Canon 2: Condemnation of the doctrines of Joachim of Flora and of Amaury.
• Canon 3: Procedure and penalties against heretics and their protectors.
• Canon 4: Exhortation to the Greeks to reunite with the Roman Church and accept its maxims, to the end that, according to the Gospel, there may be only one fold and only one shepherd.
• Canon 5: Proclamation of the papal primacy recognized by all antiquity. After the pope, primacy is attributed to the patriarchs in the following order: Constantinople, Alexandria, Antioch, Jerusalem. (It is enough to remind the reader how long an opposition preceded at Rome this recognition of Constantinople as second in rank among the patriarchal sees.)
• Canon 6: Provincial councils must be held annually for the reform of morals, especially those of the clergy.
• Canon 8: Procedure in regard to accusations against ecclesiastics. Until the French Revolution, this canon was of considerable importance in criminal law, not only ecclesiastical but even civil.
• Canon 9: Celebration of public worship in places where the inhabitants belong to nations following different rites.
• Canon 11 renews the ordinance of the council of 1179 on free schools for clerics in connexion with every cathedral.
• Canon 12: Abbots and priors are to hold their general chapter every three years.
• Canon 13 forbids the establishment of new religious orders, lest too great diversity bring confusion into the Church.
• Canons 14-17: Against the irregularities of the clergy -- e.g., incontinence, drunkenness, the chase, attendance at farces and histrionic exhibitions.
• Canon 18: Priests, deacons, and subdeacons are forbidden to perform surgical operations.
• Canon 19 forbids the blessing of water and hot iron for judicial tests or ordeals.
• Canon 21, the famous "Omnis utriusque sexus", which commands every Christian who has reached the years of discretion to confess all his, or her, sins at least once a year to his, or her, own (i.e. parish) priest. This canon did no more than confirm earlier legislation and custom, and has been often but wrongly, quoted as commanding for the first time the use of sacramental confession.
• Canon 22: Before prescribing for the sick, physicians shall be bound under pain of exclusion from the Church, to exhort their patients to call in a priest, and thus provide for their spiritual welfare.
• Canons 23-30 regulate ecclesiastical elections and the collation of benefices.
• Canons 26, 44, and 48: Ecclesiastical procedure.
• Canons 50-52: On marriage, impediments of relationship, publication of banns.
• Canons 78, 79: Jews and Moslems shall wear a special dress to enable them to be distinguished from Christians. Christian princes must take measures to prevent blasphemies against Jesus Christ.