Throughout the world the AIDS epidemic continues and even seems to accelerate in regions previously thought to be untouched. The number of cases has increased by 60% in one year. With its 15,000 seropositive persons and 35,000 cases of declared AIDS, France is the most affected of all European countries. Sexual contamination remains predominant with a relative increase of heterosexual transmissions. However, particularly in the South, transmission is prevalent in intra-venous drug addicts. In all cases worldwide it is the socially deprived, marginal and fragile populations which are the most vulnerable. Various previsions are possible in France, depending on the prophylactic measures applied. In any event, the number of seropositive subjects should be levelling out at the end of this decade, and the prevalence of the disease should stabilized at between 15,000 to 20,000 patients. At present, the cost of AIDS exceeds 5.5 billion francs.