Since the second half of the 19th century, the growing development of the medical-hygienist movement and its indissoluble combination with the eugenics movement, promoted in Chile the gradual institutional implementation of measures aimed at knowledge, treatment and eradication of gonorrhoea, syphilis and sort chancre, variants of the so-called shameful diseases, conceived as diseases of social importance since the 1920s. In this article we seek to know the medical-legal assessment of the transmission of these conditions, during the verification of sexual aggressions typified as rape, in Santiago and Valparaiso - main cities of the country - between 1890 and 1920. After considering the medical knowledge and moral perspectives from which the contagions and the sexual crimes treated, as well as their forensic assessment, the practical implementation of these provisions in judicial proceedings is analyzed.