The current sexually transmitted disease (STD) epidemic in adolescents has led to concern about the potential for spread of the human immunodeficiency virus (HIV). In 1988, a total of 5514 students in first-year community college and university classrooms across Canada were surveyed to assess STD/HIV-related knowledge, attitudes, and risk behavior. The students' mean age was 19.7 years; the male-to-female ratio was 1:1.4. Students knew more about HIV/acquired immunodeficiency syndrome than other STDs. Of the 74.3% of the men and 68.9% of the women who were coitally active, 14.3% of the men and 18.6% of the women had participated in anal intercourse and 5.5% reported a previous STD. Only 24.8% of the men and 15.6% of the women always used a condom during sexual intercourse. Among the 21.3% of the men and 8.6% of the women with 10 or more partners, regular condom use was reported in only 21% and 7.5%, respectively. In this subgroup, anal intercourse was practiced by 26.9% of the men and 34.8% of the women, and previous STD was reported by 10.6% and 24.2%, respectively. Factors associated with not using a condom included number of sexual partners, embarrassment about condom purchase, difficulty discussing condom use with a partner, use of oral contraceptives, insufficient knowledge of HIV/STDs, and the belief that condoms interfere with sexual pleasure. These factors are potentially amenable to change. Effective, behaviorally focused educational programs are needed to improve condom use and reduce STD/HIV risk.