The cause of sexually acquired genital ulceration was studied in 240 consecutive migrant mineworkers attending a sexually transmitted disease clinic in Carletonville, Transvaal. Chancroid proved to be the most common cause of genital ulcer disease, with Haemophilus ducreyi being isolated from 164 patients (68%). In 60% of cases the disease was locally acquired and in the remaining 40%, the infection was acquired in Lesotho, Botswana, Natal, Transkei and Malawi. Syphilis was diagnosed in 62 patients (26%), lymphogranuloma venereum in 16 (7%), genital herpes in 8 (3%) and granuloma inguinale in 1. No cause of ulceration could be found in 31 patients (13%). Mixed infections were documented in 41 patients (17%). Diagnosis of the cause of genital ulcer disease is not possible without relatively sophisticated laboratory support; however, simplified strategies for management and treatment have been developed.