High-risk sexual behavior among heterosexual undergraduates at a midwestern university.

Approximately 80% of a self-selected sample of 593 heterosexual undergraduate college students studied at a large Midwestern state university in 1988 had ever experienced penile-vaginal or penile-anal intercourse. One-fifth of the 477 sexually experienced women and men said they had had heterosexual and intercourse. The mean age at first vaginal intercourse was 17, while the mean age at first anal intercourse was about 18.5. Although less than four years, on average, had elapsed since the respondents' first vaginal or anal intercourse, females reported having had an average of 5.6 sexual partners, and males reported an average of 11.2 partners.