Africa is the continent most severely affected by the pandemic of immunodeficiency viruses (HIV-1 and HIV-2). Nowadays (1990), at least 3 million individuals are infected and about 300,000 cases of acquired immunodeficiency syndrome (AIDS) have been recorded. HIV infections started in the seventies as sporadic cases in remote areas and spread throughout black Africa where they are now epidemic, with high seroprevalence (1p. 100-20 p. 100), even in the general population. Due to heterosexual transmission, the groups at highest risk are female prostitutes and their customers and people with genital ulcers and/or sexually transmitted diseases (STDs). The vertical infection rates remain uncertain but may be estimated at 40 to 65 p. 100 of pregnancies in HIV-infected mothers. Blood transfusions are the third mode of infection because of high demands for blood (sometimes not tested) arising from severe anaemias in children (malaria and sickle cell anaemia), in pregnant women and in patients needing surgery. STDs causing ulcers undoubtedly are cofactors in the invasion by HIV, while the most important cofactors in AIDS progression are recurrent STDs, chronic activation of the immune system and repeated pregnancies that activate HIV-infected lymphocytes. The minimum mortality rate of AIDS is about 1 in 5000. Spatial, cultural and demographic factors should also be taken into consideration for all AIDS control programmes which must be integrated into the primary health care systems of African states.