Background: The prevalence of acne among adolescents appears to vary geographically. This study was therefore undertaken to describe the prevalence rate of acne among Danish adolescents and to study the possible influence of oral contraceptives (OC) and tobacco smoking on disease prevalence and severity. Both have been suggested to influence acne and are therefore potential confounders in studies of acne prevalence. Methods: A random sample of 186 15- to 22-year-old subjects participating in a population-based study of allergic diseases in Copenhagen County were also examined for acne. Questionnaire data on demographic variables, acne problems, smoking status and use of OC were recorded, and acne was graded according to the Leeds scale. Results: The prevalence of clinical acne (Leeds score >1) was 40.7% for men and 23.8% for women (odds ratio, OR, acne vs. no acne: 0.46, 95% confidence interval, CI: 0.24-0.85). Acne was perceived as a personal problem by 37.6% of all subjects, and this was associated with clinical acne (OR: 5.5, 95% CI: 2.7-10.9). The use of OC was associated with a significantly lower prevalence of acne (OR: 0.32, 95% CI: 0.11-0.86), while the use of tobacco smoking was not significantly associated with acne (OR: 0.54, 95% CI: 0.17-1.78). Conclusion: In congruence with recent reports from other countries, the prevalence rate of acne among adolescents was found to be lower than previously described in older reports. In this population, the use of OC was associated with a lower prevalence of acne.