This article is a study of different historiographical traditions related to the campaign against Persia by Emperor Julian of Rome (363). The western tradition was essentially based upon memories of those who participated in the campaign, which makes it the most reliable one, yet the presentation of facts depended on whether the writer was heathen or Christian. In the former case the text tended to be in favour of Julian, whereas in the latter he was put to blame. Besides that, there was a Syriac Christian tradition which had something in common with the Christian tradition of the West, but seems to rely upon stories told by those who merely heard about the campaign without being involved in it. Due to that, the Syriac tradition included a number of stories not confi rmed by firsthand evidence. Later on, the Syriac tradition passed to Muslim historians, who combined it with stories of the Arabs fight against Iran in the 4 century. Finally, there was a Persian tradition, of an entirely legendary nature, which applied a story of an earlier triumph over the Romans to the struggle against Emperor Julian.