The purpose of this work was to determine whether overweight in youth with mild-to-moderate asthma occurs with increased frequency and is accompanied by impaired psychological functioning.The interrelationships among BMI and demographic and psychological characteristics were examined in 1005 children (aged 5-12 years) enrolled in the Childhood Asthma Management Program and seen for repeated visits over 4 1/2 years.Baseline rates of overweight (BMI for age: > or = 95th percentile) were comparable, but rates of overweight risk (BMI for age: 85th to < 95th percentile) among children in the Childhood Asthma Management Program were elevated in comparison with the general population of children in the United States. Rates of overweight and overweight risk did not increase over the course of the longitudinal study. Overweight and overweight risk were more frequent among black and Hispanic than white children, although they were not higher relative to same-race groups in the general population. Overweight at baseline was associated with lower IQ, more social withdrawal, and greater internalized psychological distress. As the children became older, the overweight group demonstrated increased evidence of behavior problems and decreased physical activity.This study identifies an increase in overweight risk but not overweight in children with mild-to-moderate asthma. Comorbidity between asthma and overweight may be underestimated, because children with severe asthma and those from impoverished backgrounds were not represented in this sample. For the 14% of children who were overweight, some associated psychological difficulties were present in childhood, and additional problems were seen during adolescence. These results suggest a need for programs that encourage greater vigilance and intervention for overweight children with asthma.