The prevalence of overweight and its association with demographic, socioeconomic, behavioral, and biological variables were evaluated. The sample included 810 adolescents (10-19 years of age) living in the urban area of Pelotas, a southern Brazilian city. Overweight was defined as a body mass index > or = the 85th percentile, according to sex and age, and compared to the First National Health and Nutrition Examination Survey, following the WHO recommendation for adolescents. A clustering sampling strategy was used, and both the crude and adjusted analyses (Poisson Regression) took this strategy into account. The prevalence of overweight was 19.3% (95%CI: 16.6-22.0) and there was no difference between the sexes. The following groups presented a greater probability of being overweight: those classified in the wealthiest socioeconomic groups, those who had dieted to lose weight within the previous 3 months, those who watch 4 or more hours of television per day, and those who have less than 3 regular meals per day. After stratification by gender, high socioeconomic level was associated with greatest risk of overweight among boys. Dieting to lose weight during the previous 3 months, 4 or more hours of television viewing per day, and less than 3 formal meals per day were risk factors for overweight among girls.