The article aims to examine Maimonides’ investigation of leprosy. Re-reading the passages in Leviticus in which the issue is dealt with, Maimonides insists in his Mišneh Torah on the punitive scope of leprosy: it is simply the punishment that, following a series of warnings, God inflicts on those who have been guilty of the sin of turpitude. The strictly moral dimension is complemented by something else, however, in the Guide of the Perplexed, in which Maimonides attempts to explain the epidemic (...) phenomenon of leprosy in scientific terms, moving beyond the categories of impurity and recovery of purity that had guided him in his analyses up to that point. (shrink)