The works of medicine that Constantine the African translated from Arabic into Latin in eleventh-century Italy had far-reaching effects on the Latin West: they introduced a wide range of Latin thinkers to the philosophical richness of the Galenic tradition, and they dramatically reshaped both medical theory and practice. But for all his importance, much about Constantine himself remains murky: our earliest biographical sources are conflicting and lacunose, while the information Constantine himself provides is no less problematic. In this paper, I will show how the close examination of Constantine’s texts (and his handbook of practical medicine, the Viaticum, in particular) allows us to gain a clearer sense of several aspects of Constantine’s identity. I will argue, for example, that when we compare the text of the Viaticum to its Arabic source, we can reconstruct Constantine’s religious background with greater certainty than has hitherto been the case. At the same time, I will also briefly introduce the Viaticum’s manuscript tradition and explore how the linguistic peculiarities preserved in Constantine’s earliest manuscripts may provide us with insights into the realities of Constantine’s Arabic-Latin bilingualism.