Medieval medical views on homosexuality are outlined. Three theories seem to have been present. The first considers homosexuality as a nasty psychological phenomenon that ought to be punished rather than treated. The second theory suggests that an abnormal sensory innervation to the penis requires intense sensory input to achieve sexual satisfaction. A third congenital theory proposes that homosexuality results when the maternal sperm prevails over the paternal sperm. The most important proponent of the first theory was Avicenna (Ibn-Sîna, 980-1037 A.D.); a literal translation of the relevant chapter from his Canon of Medicine is given.