Pediatric overweight is a serious health problem in the United States. It is speculated that increasing levels of sedentary behavior may be contributing to this problem. However, few studies have investigated factors that influence sedentary behavior and body mass index (BMI). PURPOSE The purpose of this study was to assess demographic, psychosocial, and environmental correlates of sedentary behavior and BMI in a sample of 192 children. METHODS Ninety-eight Hispanic and 94 White children ranging in ages from 10–13 years (M = 11.2, SD +0.8) participated in this study. BMI was calculated via the quetelet index employing height and weight data. Using CDC and Prevention growth charts, children's overweight and at risk for overweight were defined using age-and sex-specific percentile of body mass index. An instrument adapted from the Amherst Health and Activity Study was used to assess psychosocial and environmental factors (i.e., enjoyment of physical education, social support and neighborhood characteristics) associated with sedentary behavior. Sedentary behavior was assessed by the reported amount of time spent in various behaviors (e.g., watching TV, videos, playing computer games, doing arts/crafts, doing homework, reading, or talking on the phone). RESULTS Ethnic differences in BMI and percentage of body fat were observed; with Hispanic children exhibiting higher BMI and body fat than White children. Girls had higher percentage of body fat than boys, but no gender differences were found on BMI. Findings from the hierarchical linear regression analysis indicate that age and acculturation predicted sedentary behavior; whereas, ethnicity, number of TV's in the household and the enjoyment of physical education predicted BMI. CONCLUSION These findings revealed the importance demographic and psychological factors in predicting sedentary behavior and BMI.