To assess the effects of maternal overweight and obesity as risk factors for overweight and obesity in Mexican school-age children (5 to 11 years old) who participated in the National Nutrition Survey 1999 (NNS-99). Information obtained by the NNS-99 was used to evaluate the relationship between maternal overweight and obesity and overweight or obesity in school-age children. Multivariate logistic regression analysis was used. A total of 9 259 children were studied. The prevalence of overweight or obesity was 19%, according to the criteria suggested by Cole.Thirty-nine percent of mothers were overweight and 26.4% were obese. After controlling for age, gender, and other sociodemographic characteristics, children of overweight mothers had a 1.9 times higher risk of being obese (95%CI 1.62-2.18), and children of obese mothers had a 3.4 times higher risk of being obese (95%CI 2.96-4.00), compared to children of mothers with normal BMI. Maternal overweight and obesity are risk factors for overweight or obesity in Mexican school-age children. Interventions to prevent obesity in children should be aimed towards promoting family lifestyle changes and modifying obesigenic environments.