Aim: To describe sexual behaviour as reported by 17-year-old boys in Sweden. Methods: The national cross-sectional SAM 73–90 questionnaire survey was performed in 1990, and comprised 2% of students and school non-attenders born in 1973. The respondents included 814 students and 92 non-students, response rates 90.6% and 40.2%, respectively. Data from the two groups are treated separately. Results: In the student group, 54.2% of boys had experienced vaginal intercourse and 16.7% were “early starters” with coitarche before 15 y of age. Independent predictors for coital experience were the vocational study programme OR (odds ratio) 1.91 (95% CI 1.31–2.78), early puberty OR 1.69 (95% CI 1.11–2.57), use of tobacco OR 5.32 (95% CI 2.43–11.7) and alcohol OR 4.09 (2.79–5.98). Sexually transmitted infections (STIs) were reported by 4.1% of coitally active student boys, and impregnating a girlfriend by 4.3%. Of the early starters, 14.6% reported having more than 10 sex partners as compared with 2.5% of the later starters (p > 0.0001) and this was predictive of STI, OR 5.4 (95% CI 1.5–19.7). First-date intercourse more than twice was predictive of pregnancy, OR 14.4 (95% CI 3.8–54.5). Among school non-attenders, 74.2% reported coital experience, 33.7% were early starters, and 12.5% had impregnated a girl.
Conclusion: Boys' early sexual experience was related to early puberty, and to general adolescent risk-taking behaviour. Early coitarche per se was not predictive of STI or pregnancy, but the associated high number of “lifetime” sexual partners and first-date intercourse were predictive factors. School non-attenders constituted a group at risk.