OBJECTIVE: To assess whether intake of fruits and vegetables was associated with change in body mass index (BMI) among a large sample of children and adolescents in the United States. DESIGN: Prospective cohort study of children and adolescent who were 9-14 y of age in 1996, when the study began. SUBJECTS: The subjects included 8203 girls and 6715 boys in an ongoing cohort study who completed at least two questionnaires between 1996 and 1999. MEASUREMENTS: Fruit and vegetable intake was assessed in 1996-1998 with a validated food frequency questionnaire designed specifically for children and adolescents. The outcome measure was change in age- and gender-specific z-score of BMI (kg/m2). Self-reported weight and height, which were used to calculate BMI, were collected annually from 1996 to 1999. RESULTS: During 3 years of follow-up, annual changes in BMI were slightly greater among the boys than the girls. After controlling for Tanner stage of development, age, height change, activity and inactivity, which are known or suspected predictors of change in BMI, among the girls there was no relation between intake of fruits, fruit juice, or vegetables (alone or combined) and subsequent changes in BMI z-score. Among the boys, intake of fruit and fruit juice was not predictive of changes in BMI, however, vegetables intake was inversely related to changes in BMI z-score (β per serving = -0.003). However, after adjusting for caloric intake, the magnitude of the effect was diminished and no longer significant. CONCLUSION: Our results suggest that the recommendation for consumption of fruits and vegetables may be well founded, but should not be based on a beneficial effect on weight regulation.