The reign of Alexander III was one of the most laborious pontificates of the Middle Ages. Then, as in 1139, the object was to repair the evils caused by the schism of an antipope. Shortly after returning to Rome (12 March, 1178) and receiving from its inhabitants their oath of fidelity and certain indispensable guarantees, Alexander had the satisfaction of receiving the submission of the antipope Callistus III (John de Struma). The latter, besieged at Viterbo by Christian of Mainz, eventually yielded and, at Tusculum, made his submission to Pope Alexander (29 August, 1178), who received him with kindness and appointed him Governor of Beneventum. Some of his obstinate partisans sought to substitute a new antipope, and chose one Lando Sitino, under the name of Innocent III. For lack of support he soon gave up the struggle and was relegated to the monastery of La Cava. In September, 1178, the pope in agreement with an article of the Peace of Venice, convoked an ecumenical council at the Lateran for Lent of the following year and, with that object, sent legates to different countries. This was the eleventh of the ecumenical councils. It met in March, 1179. The pope presided, seated upon an elevated throne, surrounded by the cardinals, and by the prefects, senators, and consuls of Rome. The gathering numbered three hundred and two bishops, among them several Latin prelates of Eastern sees. There were in all nearly one thousand members. Nectarius, abbot of the Cabules, represented the Greeks. The East was represented by Archbishops William of Tyre and Heraclius of Caesarea, Prior Peter of the Holy Sepulchre, and the Bishop of Bethlehem. Spain sent nineteen bishops; Ireland, six; Scotland, only one- England, seven; France, fifty nine; Germany, seventeen- Denmark and Hungary, one each. The bishops of Ireland had at their head St. Laurence, Archbishop of Dublin. The pope consecrated, in the presence of the council, two English bishops, and two Scottish, one of whom had come to Rome with only one horse the other on foot. There was also present an Icelandic bishop who had no other revenue than the milk of three cows, and when one of these went dry his diocese furnished him with another.

Besides exterminating the remains of the schism the council undertook the condemnation of the Waldensian heresy and the restoration of ecclesiastical discipline, which had been much relaxed. Three sessions were held, on 5, 14, and 19 March, in which twenty-seven canons were promulgated, the most important of which may be summarized as follows:

• Canon 1: To prevent schisms in future, only the cardinals should have the right to elect the pope, and two-thirds of their votes should be required for the validity of such election. If any candidate, after securing only one-third of the votes, should arrogate to himself the papal dignity, both he and his partisans should be excluded from the ecclesiastical order and excommunicated.
• Canon 2: Annulment of the ordinations performed by the heresiarchs Octavian and Guy of Crema, as well as those by John de Struma. Those who have received ecclesiastical dignities or benefices from these persons are deprived of the same; those who have freely sworn to adhere to the schism are declared suspended.
• Canon 3: It is forbidden to promote anyone to the episcopate before the age of thirty. Deaneries, archdeaconries, parochial charges, and other benefices involving the care of souls shall not be conferred upon anyone less than twenty-five years of age.
• Canon 4 regulates the retinue of members of the higher clergy, whose canonical visits were frequently ruinous to the rural priests. Thenceforward the train of an archbishop is not to include more than forty or fifty horses; that of a bishop, not more than twenty or thirty; that of an archdeacon, five or seven at the most- the dean is to have two.
• Canon 5 forbids the ordination of clerics not provided with an ecclesiastical title, i. e. means of proper support. If a bishop ordains a priest or a deacon without assigning him a certain title on which he can subsist, the bishop shall provide such cleric with means of liveli hood until he can assure him an ecclesiastical revenue that is, if the cleric cannot subsist on his patrimony alone.
• Canon 6 regulates the formalities of ecclesiastical sentences.
• Canon 7 forbids the exaction of a sum of money for the burial of the dead, the marriage benediction, and, in general, for the administration of the sacraments.
• Canon 8: The patrons of benefices shall nominate to such benefices within six months after the occurrence of a vacancy.
• Canon 9 recalls the military orders of the Templars and the Hospitallers to the observation of canonical regulations, from which the churches dependent on them are in no wise exempt.
• Canon 11 forbids clerics to receive women in their houses, or to frequent, without necessity, the monasteries of nuns.
• Canon 14 forbids laymen to transfer to other laymen the tithes which they possess, under pain of being debarred from the communion of the faithful and deprived of Christian burial.
• Canon 18 provides for the establishment in every cathedral church of a school for poor clerics.
• Canon 19: Excommunication aimed at those who levy contributions on churches and churchmen without the consent of the bishop and clergy.
• Canon 20 forbids tournaments.
• Canon 21 relates to the "Truce of God".
• Canon 23 relates to the organization of asylums for lepers.
• Canon 24 consists of a prohibition against furnishing the Saracens with material for the construction of their galleys.
• Canon 27 enjoins on princes the repression of heresy.