The prevalence, severity and disability related to facial acne (comprising acne on the head and neck) was assessed in a randomized sample of 2491 students (aged 4-18 years) from schools throughout the State of Victoria in Australia. Students were diagnosed clinically by a dermatologist or dermatology registrar. The overall prevalence (including 4-7 year olds) was 36.1% (95% confidence intervals, CI 24.7-47.5), ranging from 27.7% (95% CI 20.6-34.8) in 10-12 year olds to 93.3% (95% CI 89.6-96.9) in 16-18 year olds. It was less prevalent among boys aged 10-12 years than girls of the same age; however, between the ages of 16 and 18 years, boys were more likely than girls to have acne. Moderate to severe acne was present in 17% of students (24% boys, 11% girls). Comedones, papules and pustules were the most common manifestations of acne, with one in four students aged 16-18 years having acne scars. Twelve per cent of students reported a high Acne Disability Index score. This tended to correlate with clinical severity, although there was some individual variation in perception of disability. Seventy per cent of those found to have acne on examination had indicated in the questionnaire that they had acne. Of those, 65% had sought treatment, a substantial proportion of which (varying with who gave the advice) was classified as being likely to have no beneficial effect. This is the first population-based prevalence study on clinically confirmed acne published from Australia. The results show that acne is a common problem. They suggest the need for education programmes in schools to ensure that adolescents understand their disease, and know what treatments are available and from whom they should seek advice.