Heterosexual anal intercourse is rarely discussed in the scientific literature. Review of the literature suggests the silence is linked to ethnocentric discomfort about it among researchers and health care providers, coupled with the misconception that anal sex is a homosexual male practice, not heterosexual. Review of surveys of sexual practices suggest that heterosexual anal intercourse is far more common than generally realized, more than 10% of American women and their male consorts engaging in the act with some regularity. Sexually transmitted disease (STD) data, especially where only the rectum is infected with gonorrhea or other STD agents, buttresses survey data. Considerably more heterosexuals engage in the act than do homosexual and bisexual men, not all of whom participate in anal coitus. Anal intercourse carries an AIDS risk for women greater than that for vaginal coitus, just as receptive anal intercourse carries a very high risk for males. Infection with the AIDS virus is increasingly documented in women engaging in anal coitus with infected males, in America, Europe, and Latin America. Women in Western countries are less likely to continue HIV infectivity chains than are males engaging in same-gender anal intercourse.