Between 1977 and 1981, 3089 patients attended the sexually transmitted diseases (STD) clinic in Zaria, northern Nigeria. The male-to-female ratio of attenders was 6:1. Postpubertal gonorrhoea accounted for 28.1% of cases, non-specific genital infections for 22.4%, and syphilis for 1.2%. Illiteracy, polygamy, the purdah system, widespread prostitution, and inadequate facilities are factors aiding the spread of these diseases in northern Nigeria.