This research was conducted among 1000 men and 1000 women in five urban and five rural sites in Zaire to obtain information on sexual behavior, especially practices which affect the risk of HIV transmission. Mean coital frequency was 1.7 relations per week for the total population, compared to approximately 4 relations per week among the“sexually active.”One‐half of men and one‐third of women reported having changed their behavior because of AIDS. However, 18% of men reported more than one sexual partner in the past 30 days; 10% of married men and 12% of single men had visited a prostitute in the past 30 days. While condom use was higher among those who had had multiple partners and/or visited a prostitute, two‐thirds of these men reported never having used them. A small but important minority persists in high‐risk behavior despite widespread knowledge of AIDS and modes of transmission.