OBJECTIVE--To compare the frequencies of HLA antigens in patients with donovanosis and in controls. DESIGN--HLA Class I, Class II and DQ antigens were detected in patients with genital ulceration caused by donovanosis and in a control group. SETTING--City Health STD Clinic, King Edward VIII Hospital, Durban, South Africa. Participants--Sixty (47 men, 13 women) patients with donovanosis. RESULTS--HLA B57 was detected in nine of 60 (15%) with donovanosis and 75 of 1478 (5.1%) controls (RR = 3.3 chi 2 = 11.0, p = 0.001, p corrected = 0.026). CONCLUSIONS--A possible link between donovanosis and HLA B57 could be explained by coexisting alleles or immune response genes in linkage disequilibrium altering disease susceptibility.