The continuity of the Roman Empire in the East meant that Christianity developed differently there than it did in the West. The emperors in Constantinople were understood to be Christ’s representatives on earth; their palace was considered holy and was filled with relics and religious images, called icons. Emperors convened councils, appointed church officials, and regulated the income of the church. As in Rome, there was a patriarch in Constantinople, but he did not develop the same powers that the pope did in the West because there was never a similar power vacuum into which he needed to step. The Orthodox Church, the name generally given to the Eastern Christian Church, was more subject to secular control than the Western Christian Church.

Monasticism in the Orthodox world differed in fundamental ways from the monasticism that evolved in western Europe. While The Rule of Saint Benedict gradually became the universal guide for all western European monasteries, each individual house in the Byzantine world developed its own set of rules for organization and behavior. Second, education never became a central feature of Orthodox monasteries. Monks and nuns had to be literate to perform the appropriate rituals, but no Orthodox monastery assumed responsibility for the general training of the local young.

There were also similarities between Western and Eastern monasticism. As in the West, Eastern monasteries became wealthy property owners, with fields, pastures, livestock, and buildings. Since bishops and patriarchs of the Orthodox Church were recruited only from the monasteries, these religious leaders also exercised cultural influence.

Like their counterparts in the West, Byzantine missionaries traveled far beyond the boundaries of the empire in search of converts. In 863, the emperor Michael III sent the brothers Cyril (826–869) and Methodius (815–885) to preach Christianity in Moravia (a region in the modern Czech Republic). Other missionaries succeeded in converting the Russians in the tenth century. Cyril invented a Slavic alphabet using Greek characters, later termed the Cyrillic (suh-RIH-lihk) alphabet in his honor. In the tenth century, other missionaries spread Christianity, the Cyrillic alphabet, and Byzantine art and architecture to Russia. The Byzantines were so successful that the Russians would later claim to be the successors of the Byzantine Empire.