Correlates of heterosexual behavior, with a particular focus on early and high sexual activity, anal intercourse, prostitute visits, and HIV test activity, were studied. Telephone interviews were conducted with 852 randomly chosen persons who participated as controls in nationwide case-control studies of anogenital cancers in Denmark and Sweden, 1992-1998. While partner numbers and the practice of anal intercourse increased, age at sexual debut declined by 4-5 years (p < 0.001) and the maturation interval between menarche and first coitus halved (from 7 to 3 years, p < 0.001) between persons born in or before 1920 and those born in or after 1960. Women having high sexual activity were more often tested for HIV than less sexually active women, but men visiting prostitutes and those with prior STDs were not HIV tested more than other men. The increasing practice of anal intercourse, particularly among women with many partners, deserves attention, since this practice may erroneously be considered a safe sexual activity. Along with their partners, men with a history of STDs and those visiting prostitutes should be targeted in future safe sex campaigns, since these men appear to be inadequately HIV tested.