Objective: To determine the prevalence of overweight and obesity in school adolescents. Place and date: Floridablanca, Santander, Colombia; second semester of 2005. Materials and methods: Cross-sectional study among 195 students aged 11-18 years old from private or public schools. They responded a survey on demographic variables and eating habits. We estimated body mass index to determine association between explanatory variables with each one of interest variables. Results: Global overweight prevalence was 6.7% (95%CI 3.5-11.1) and to obesity 1.0% (95%CI0.1-3.6). Overweight in males was 8.6% (95%CI 3.7-16.2) and in females 4.9% (95%CI 0.1-11.0). Obesity prevalence in males was 2.1% (95%CI 0.2-7.5), whereas in females was 1.9% (IC 95% 0.2-6.9). No significant differences were found. There is association between alcohol consumption and overweight (OR 4,11; 95%CI1.10-15.58; p=0.009). Conclusion. It is necessary to continue doing research on overweight, obesity and their associated factors, with the purpose of raising and executing effective solution strategies that control their incidence and avoid them in earlier ages.