For some time, a debate has been occurring in Africa and elsewhere on the desirability of systematic testing of the population to identify carriers of the acquired immune deficiency syndrome (AIDS) virus. Large elements of the public demand such testing, but physicians are generally opposed, for several reasons. The different governments of Africa have followed the advice of the Physicians. Epidemiologists realize that a systematic screening is never complete or systematic except in theory; the existence of individuals whose disease escapes detection would pose a grave danger by causing a relaxation of vigilance and respect of rules for AIDS prevention. The AIDS diagnostic tests currently in use are indirect, and detect antibodies rather than the virus itself. Over 90% of individuals have a positive reaction within the 8 weeks following exposure, but persons exposed a week or 2 before testing would in all likelihood test negative. Such persons would be unaware that they were carriers able to infect others. The idea of systematic preoperative screening has also been abandoned by most surgeons because it would cause a false sense of security and relaxation of vigilance in seronegative cases, some proportion of whom would in fact be carriers of the disease. Maximal protective measures must therefore be adopted when treating any patient. A national screening effort would cause a similar relaxation of protective measures by the population, with perhaps tragic result. The decisive argument against systematic screening is economic. No African country currently has the funds to finance systematic screening, which could cost the equivalent of 10% of the national revenue of poor countries like Mali, Burkina Faso and Guinea. There is no cure to offer seropositive cases, and there is the danger that they would face isolation and discrimination from the rest of the society.