Since 1991 AIDS and HIV infection in the Federal Islamic Republic of the Comoros have been monitored through a network of sentinel sites including predetermined target populations. In all cases seropositivity for HIV was confirmed by western blotting after two ELISA screening tests. AIDS was diagnosed on Bangui clinical criteria and positive western blotting results. As of June 30, 1996, the cumulative number of AIDS cases reported to the World Health Organization was 7 for a prevalence of 1.4 per 100000 inhabitants. The prevalence of HIV antibodies has remained at less than 1% in target populations, i.e. women undergoing prenatal examinations, patients with newly diagnosed tuberculosis, blood donors, and patients presenting sexually transmitted diseases (STD). This low stable prevalence rate which is similar to those reported in other Indian Ocean countries is in sharp contrast with the high incidence of syphilis and STD in the region.