Objective To assess overweight/obesity of elementary schoolchildren in Campinas , São Paulo , Brazil, and its association with parental nutritional status, children's food consumption, food preferences, and level of physical activity, and familial socioeconomic status. Methods This case-control study included 509 schoolchildren aged 7 to 10 years. Body mass index Z-score was used to determine nutritional status, defining cases (>+1 Z-score) and controls (³-2 ?+1 Z-score). To address association with overweight/obesity, a conceptual model was established and used for multiple analysis, performed by logistic regression. Results The children had an overweight/obesity frequency of 39.5%. Multiple analysis adjusted for socioeconomic level showed that overweight/obese children were more likely to eat at the mall (1.55; 95%CI=1.00-2.40), have overweight and obese parents (OR=1.71; 95%CI=1.08-2.71 and OR=3.55; 95%CI=2.18-5.80 respectively), report use of passive school transport (OR=1.57; 95%CI=1.04-2.36), and consume chicken nuggets on 3 or more days per week (OR=3.03; 95%CI=1.32-6.95). Conclusion These results support the urgent need of strategies to reduce overweight/obesity and promote its prevention in schoolchildren. Moreover, intervention studies involving parents and addressing environmental factors are important for the development of effective programs.