The most brutal persecution of Christians occurred from the year 250 to 311, at the time of Emperor Diocletian. At that time a martyr death came upon many Salonian Christians such as Bishop Saint Domnio, Priest Asterius, Deacon Septimius, Tangar Anastasius and four soldiers of Diocletian's bodyguards: Telius, Antiohian, Guyana and Paulinian. We mustn't forget Saint Venancius, who, as it seems, gained the martyr crown in the last three years of Valerian's ruling, about the year 257 – 260, as well as many other important figures of faith like Saint Felix, who is mentioned in the oldest source of martyrdom by Saint Domnio, as well as many other not only Salonian martyrs, but also Istrian, the most known of whom is Saint Mauro. The main reason for the persecution was hatred towards Christians, who, having faith in God, refused to worship the Emperor and pagan deities. They did not rely on their own strength, but they completely devoted their lives to God. He was their idol, their ideal, their goal. After the Milanese edict, Christianity is equalized with other religions in the empire, and there is a start to worshipping martyrs and Cristians are focused onarranging cemeteries which thrive around the graves of martyrs. An example of such care can be seen in the earliest phases of the development of Salonian cemeterial complexes at Kapljuč, Manastirine and Marusinac. At the graves of these distinguished members of the Christian community or a local martyr, occurs a gradual development of worshipping their earthly remains, memories are built, in the beginning usually modest sites to put martyrs' bones, but later they are extended and luxuriously decorated , and thus large cemeterial basilicas develop. The purpose of being buried as close to the martyr's grave as possible is to be more certain to get that martyr for a guardian, a patron or a defender when they have to face the heavenly judge. Thus, with all justification, it can be assumed that there were martyrs for whom we have no testimony. However, credible evidence which proves that these Salonian martyrs really existed, is a mosaic in the chapel of Saint Venancius in the Lateran baptistery, on which, besides the martyrs, Saint Mauro can also be seen.