- In spite of a variety of broad-based interventions, rates of adolescent sexual intercourse remain high. Using data from a large longitudinal study, this paper provides empirical evidence of Canadian adolescent sexual activity rates by age and gender. The incidence of first sexual intercourse among those 13-15 years was higher among males than females; by ages 16-17 years, rates were the same for both genders (25%). Prevalence of sexual intercourse with age; by age 16-17 years, similar rates were reported for both genders (approximately 50%). Analysis of data over a three-year period indicated that at each age, over 80% of adolescents reported intermittent or no sexual intercourse. Different factors predicted the absence of early sexual intercourse for the two genders. These data provide useful information about Canadian adolescent sexual activity, particularly related to identifying high risk groups for targeted prevention interventions.