To evaluate physical activity, obesity and asthma, we analyzed information from children attending a racially diverse middle-class suburban school district. Physical activity in metabolic equivalents (METS) and percent body fat were related to diagnosed asthma. On average the, 636 children were 8.9 years of age, 64.0% black, and 11.8% with reported asthma. Children with asthma were more active: 6,438 versus 5,432 METs/year, p = 0.03. Logistic regression considering METs, percent fat, gender and race showed METs were a significant risk factor for asthma, odds ratio (OR) = 1.24 (95% CI 1.01-1.52, p = 0.045). Higher levels of physical activity were related to more diagnosed asthma.