We report the findings of an epidemiological study conducted between June 1989 and February 1990 on a population of leprosy patients in southern Senegal (Bignona major endemic disease sector). Two types of population were studied: patients living in urban areas and inmates of leprosaria. The global HIV seroprevalence (HIV 2 in all cases) of the leprosy-patient population was 1.15% (3/257): 0.8% (1/130) for the urban group and 1.5% (2/127) for the leprosaria. The seroprevalence rate does not differ significantly from that for the control group studied and for blood donors (1/221). The diagnosis of leprosy in the seropositive subjects had been established before 1980. None of them showed any sign of relapse. The immunodepression associated with the presence of HIV was only moderate: it was reflected in a lowering of the CD4 count and of the CD4/CD8 ratio, but with no clinical sign of AIDS.