The classification of non-heterosexuality has changed considerably over the past century. Once considered as medical conditions attracting legal complications and serious social stigma, expressions of non-heterosexuality are now broadly considered to be normal variations of human sexuality. The historical inclusion of homosexuality in the psychiatric literature may still have implications for how sexual orientation is viewed today, including the ongoing treatment of homosexuality as an illness despite its delisting from medical diagnostic nomenclatures. This discussion paper explores the historically recorded diagnostic classification of homosexuality, reviews the processes that led to the reclassification in the nomenclature and closes with a commentary for current implications of this medical legacy.