Synod held in St. Peter’s Basilica from 6 November until 4 December 963, under the authority of the Holy Roman Emperor, Otto I to confront the irregularity of John XII's papacy

Composition of the synod

• Holy Roman Emperor Otto accompanied by a number of dukes and counts of Germany and Italy
• Italy
  • The Deacon Rodalph, representing the Patriarch of Aquileia, the highest ecclesiastical authority in the west after the pope.
  • Walpert, Archbishop of Milan
  • Peter IV, Archbishop of Ravenna
  • Hubertus, Bishop of Parma
  • Liutprand, Bishop of Cremona
  • Sico, Bishop of Ostia
  • Teophylactus, Bishop of Praeneste
  • Benedictus, Bishop of Silva Portus
  • Giovanni, Bishop of Sabina
  • Leo I, Bishop of Velletri-Segni
  • The Bishop of Albano
  • The bishop of Silva Candida
  • The Bishop of Gabium
  • The Bishop of Forum Claudii
  • The Bishop of Bleda
  • The Bishop of Nepi
  • The Bishop of Caere
  • The Bishop of Tibur
  • The Bishop of Alatri
  • The Bishop of Anagni
  • The Bishop of Treviso
  • The Bishop of Ferentino
  • The Bishop of Norma
  • The Bishop of Veroli
  • The Bishop of Sutri
  • The Bishop of Narni
  • The Bishop of Gallese
  • The Bishop of Falerii
  • The Bishop of Orta
  • The Bishop of Terracina
• Germany and West Francia
  • Adaldag, Archbishop of Hamburg-Bremen
  • Landward, Bishop of Minden
  • Otgar, Bishop of Speyer
• Cardinal-priests: There were 13 cardinal priests who attended the synod, one of whom was the future Pope Benedict V. An unknown number had fled with Pope John XII. Their Titular churches were:
  • Santa Balbina
  • Basilica di Sant'Anastasia al Palatino
  • San Lorenzo in Damaso
  • San Crisogono
  • Santa Susanna
  • Saint Equitius
  • Saint Pammachius
  • Saint Calixtus
  • Santa Cecilia in Trastevere
  • San Lorenzo in Lucina
  • San Sisto Vecchio
  • Santi Quattro Coronati
  • Santa Sabina
• Other participants
  • Heads of the Roman militia, led by Peter Imperiola
  • officers of the papal court
  • Deacons, Regionarii, notaries and the Primicerius of the Schola cantorum
  • Roman nobles aligned to the imperial party:
    • Stephen, son of John the Superista
    • Demetrius, son of Meliosus
    • Crescentius of the Marble Horse
    • Giovanni de Mizina
    • Stephano de Imiza
    • Theodorus de Rufina
    • Giovanni de Primicerio
    • Leo de Cazunuli
    • Pietro de Cannapara
    • Benedict and his son Bulgamin