The effectiveness of a multidimensional Canadian sex education programme was evaluated using 240 Grade Nine students. The intervention was offered by representatives from various community groups and involved instructional classes on anatomy/physiology of the reproductive system and sexually transmitted infections, a video and group discussion on healthy relationships, a form of "peer education" and discussion on teen pregnancy and HIV/AIDS, as well as a parent workshop and newsletter on teen sexuality. Respondents in the intervention and control groups completed a self-administered questionnaire at baseline and one month after the programme. Compared with the control group, students in the intervention group showed positive changes in the areas of knowledge, sex-role attitudes, sexual interaction values, and the perception that birth control is important. These results suggest that a collaborative effort of outside professionals from various community organisations and involvement of "peer educators" to provide sexual health education in Grade Nine high school classes may be a useful strategy. (Contains 9 tables and 3 notes.)