This paper presents the methodology and results of the implementation of a Surveillance System for Non-Communicable Disease Risk Factors in Adolescents. A random sample of 8th-grade students (n = 1,684) enrolled in municipal schools in Rio de Janeiro, Brazil, was studied. Students were asked to complete a confidential questionnaire on food consumption, physical activity, sedentary leisure-time activities, and tobacco consumption. Prevalence estimates of risk factors were calculated for the entire sample and by gender. Non-response rates ranged from 1.1 to 8.9%. The findings included low consumption of fruits (45.8%) and vegetables (20.0% and 16.5% for salads and cooked vegetables, respectively), regular consumption of soft drinks (36.7%) and candies (46.7%), extensive time on TV, computer, and videogames (71.7% spend at least 4h/day at these activities), low frequency of regular physical activity (40%), and 6.4% prevalence of smoking. Girls showed less physical activity and more smoking. The system appeared to be feasible and indicated high prevalence of risk factors for non-communicable diseases.