The aim of this study is to describe physical activity practice among Brazilian adolescents by using data from the National Adolescent School-based Health Survey (PeNSE) collected in all state capitals and the Federal District in 2009. The sample included students of the ninth year (n=60,973). It was investigated the physical activity practice seven days prior to the interview, including transportation mode, physical activity practice inside and outside the school and participation in Physical Education classes. Adolescents were classified as active if performing >or= 300 min/wk of physical activity. The proportion of active adolescents was 43.1%; this figure was higher among boys (56.2%) as compared to girls (31.3%). Only half of the adolescents (49.2%) reported that had two or more Physical Education classes in the week prior to the interview. Also, 79.2% reported watching TV for two or more hours per day. Our data indicate a low proportion of active adolescents and of regular Physical Education classes, and a high prevalence of sedentary behavior. These data might be used as a baseline for the monitoring of physical activity among adolescents in Brazil, but already suggests the need of interventions for the promotion of physical activity among Brazilian adolescents.