The incidence and mode of presentation of trichomonal urethritis in Nigerian males have benn investigated. Nineteen (10.6%) out of 179 patients presenting with non-gonococcal urethritis were found to harbour the parasite. The commonest symptoms were urethral discharge and/or urethral irritation. The usefulness of examining wet preparations of the urethral exudate in diagnosis is stressed. No significant difference has been found between the incidence of the condition in Nigerians as compared with other ethnic groups. Attention is drawn to the possibility of T. vaginalis playing a role in male infertility, its superinfection in longstanding urethritis is stressed, and the therapeutic efficacy of metronidazole is appraised.