Suggestions which came up at a 1941 Northern Nigeria Chiefs’ Congress included the need to arrest, register every unmarried young female living within the Northern region, and if such girls came from outside the region, they should be deported. Around this period, the frequent report of sexually transmitted diseases, especially syphilis and gonorrhea drew public attention to the commercialization of sex in colonial Northern Nigeria. While the government increased its effort to deal with STDs, it also mandated native authorities to regulate the moral behavior of the citizens. The chiefs blamed the spread of STDs on the immigration of single women from Southern Nigeria and areas around the Niger/Benue confluence. Although it was relatively difficult to implement any of the suggestions, the views pointed to certain concerns over gender relations as well as the dangers that were associated with unmarried women. This paper focuses on the STD/prostitution/morality debate and the implication for gender and ethnic relations in colonial Northern Nigeria.