A survey of the social perception of AIDS and its prevention was carried out in December 1987 in a representative sample of the adult population of the Paris region (France). A significant part of the general public still holds misconceptions about transmission by casual contact and blood donation. Misbeliefs about modes of transmission clearly encourage individuals' willingness to stigmatize AIDS patients and to support the most coercive measures of prevention (such as quarantine). Advertizing efforts to promote use of condoms, sexual education in schools, and systematic HIV screening for pregnant women are the only measures which create a broad consensus independently of sociocultural differences. Socioeconomic status and even religious or political beliefs strongly influence public opinions toward other preventive measures.