Differences between heterosexuals who have or have not engaged in anal intercourse were analyzed. Though anal intercourse is widely recognized as an activity that greatly increases the risks for HIV transmission, it has received little attention in heterosexual populations. A questionnaire was mailed to a random sample of university students, a population in which many people engage in vaginal intercourse with several partners each year. The three largest minorities were randomly oversampled in order that all four major ethnic/racial groups could be statistically evaluated for possible differences. Almost 23% of nonvirgin students had engaged in anal intercourse. Regression analysis indicated that people who had participated in anal intercourse were more likely than people without anal experience to have been younger at first vaginal intercourse, to be older when the data were collected, to have engaged in vaginal intercourse in the last three months before data collection, to be more erotophilic, to use less effective contraceptive methods, and to have used no condom at last coitus. Overall, people who engage in anal intercourse take more sexual risks when engaging in vaginal intercourse than do people without anal experience. No major ethnic/racial differences were detected. Sexologists have not explored anal sex in much detail, hence we have been weak in educating those 20 to 25% of young adults who are not reluctant or (inhibited about) exploring anal intercourse. As young adults use condoms less for anal than vaginal intercourse, they have not learned enough about the risk of anal sex.