To this day, cocaine is widely perceived as an aphrodisiac and often associated with prostitution and sexual deviance. This article traces the origins of this popular image in late nineteenth and early twentieth century German medicine. It reconstructs how medical discourses about neurasthenia, homosexuality and psychoactive substances came to equate narcotic-use and deviant sexual behavior as factors that both caused and could result from sexual and nervous disorders. As this article also shows, this presumed causal relationship in turn shaped medical perceptions of cocaine-use among homosexuals and prostitutes in urban red-light districts in the Weimar Republic, which reinforced medicine's neglect of cocaine-consumption among socially integrated groups. While pharmacological and physiological knowledge have changed drastically since then, remnants of this motif live on to this day.