For most of the twentieth century the major problem addressed by scholarship on both Roman Mithraism and the Iranian god Mithra was the question of continuity. Did Mithra-worship migrate from Iran to the Roman Empire in some institutional form or was Mithraism invented in the West (with a few Iranian trappings) as a new institution altogether? At the start of the twenty first century, this issue appears to be less central to the concerns of scholarship on Western Mithraism, but it remains important nevertheless, and obviously it must be the lens through which Mithraism is examined in this article. The first task, though, is to describe the Mithras cult as it did in fact develop in the West, and in so far as we can reconstruct it objectively from its material remains. Reconstruction is not easy, since no ancient literary works about Mithraism and no substantial sacred texts from Mithraism have survived.