Christianity appeared in the Greco-Roman world in the Mediterranean, at a time when he was plunged into an abyss of religious ferment. At that time there were many cults, including the cult of the Roman gods and worship the gods of those cities and states, which are included in the structure of the Roman Empire. Of crucial importance was attached to the cult of the ruler. Widespread type mystery cults were dedicated to one or the other Greek gods. They were intertwined with the worship of a certain deity, who was killed by their enemies, and then he was revived from the dead. Such cults kept secret from outsiders, those who knew the secret belief that, in exercise of such rituals, they are involved in the death of a deity and, through his coming to life their dead gain eternal life. A different tradition of religion, Hermeticism, promised his supporters liberation from vices of the flesh and eternal life. Christianity denied the recognition of the pagan gods as well as the ruler. Christianity has had some features of similarity with mysterial rituals, but differed significantly from them - in particular, the fact that it is not revered mythological hero, a real historical figure whose life and teachings have been the subject of worship and faith. Christian doctrine and was significantly different from what we could offer mystery cults. Christianity is partly borrowed its terminology database of Greek philosophy, but its meaning - the belief that in Christ the eternal God became man, suffered death on the cross and then rose from the dead - it had nothing to do with any available at that time insightful systems. Early Christianity in many ways different from other religions as well as from formal worship, so his followers faced with the eternal persecution by the majority of people and the authorities have put Christianity is outlawed. But the number of Christians multiplied, and the rulers take serious measures in order to force them to renounce their faith. During the 3-in. Two of the Emperor - Decius and Valerian his successor - have done everything possible to forever put an end to this belief. In the early 4 th century, Diocletian began the widest and most terrible of all the persecution of Christians. But for 5 centuries that followed the crucifixion of Jesus Christ, a large population of the Roman Empire, not excluding the rulers become Christian. Three hundred and twelfth year of Emperor Constantine the Great became a Christian, to obey such an example 3-th of his sons, who later became rulers. Attempt nephew of Constantine, the ruler of Julian (who was nicknamed "The Departed"), failed to revive paganism. At the end of the 5 th century. Christianity became the dominant religion in Armenia, the Christian communities arose in the Persian Empire, in India and the Germanic peoples on the northern frontier of the Roman Empire. In the 1st generation of Christians there were several well-known missionaries, the best of whom believe the two apostles Paul and Peter. They and their less famous contemporaries preached Christianity among the predominantly Greek-speaking population throughout the empire. Among large cities, Christianity spread to small towns, and from there - in the countryside. Among the reasons which prompted the majority of the people of the Roman Empire to Christianity, are the following: 1) a gradual decay and disintegration of the cultural heritage, 2) the adoption of Christianity by Constantine and his successors, and 3) that the Christian faith, people of all classes and ethnic groups are taken into one, the overall association and the fact that this religion could be adapted to specific national traditions, and 4) the unequivocal commitment of the church's own beliefs and moral qualities of all members, 5) patriotism, religious martyrs.