Background and purpose: Acne vulgaris is a very common cutaneus disorder as chronic inflammation of sebaceous glands of the skin of face, chest and back that affects everyone almost once in life time. The goal of this study was to determine the prevalence of Acne vulgaris in schools of Sari in 2003-2004.Materials and Methods: In this cross-sectional-analytical study, stratified sampling method was used, to divide male and female groups, and then a multistage random sampling was performed. All of the samples were examined for Acne vulgaris by a dermatologist, according to reliable clinical and diagnostic criteria. Questionnaires containing demographic, epidemiologic and clinical variables were filled in accordingly.Results: Two hundred samples from each stratum (400 overall), with a mean age of 15±1.51 and range of 12 of 18 years were selected. One hundred and sixty three subjects (40.75 %) were affected, 50 (30.6 %) male and 113 (69.4 %) female with the condition being mild in 150 (92.02 %) and moderate in 13 (7.98 %) of the patients. The highest prevalence was in 16 years olds 52 (62.65 %) and the lowest was 2 (7.4 %) in 12 years olds.Conclusion: According to the relatively high prevalence of Acne vulgaris in puberty, especially in females, performing continuous epidermiologic studies can be a good step for interventional studies, and preventing psychologic problems caused by the disease and hence increasing the health level of the community.