The active intervention is designed to prevent excessive weight gain by promoting healthy eating habits and increasing physical activity. An alternative intervention (comparison group) promotes general self-esteem and social efficacy. The main outcome measure is the difference between the two treatment groups in the change in BMI at 2 years. Three hundred and three girls have been randomly assigned to receive the test intervention (n = 153) or the alternative intervention (n = 150). The two groups do not differ in baseline characteristics. At the time of enrollment, the mean age was 9 years, the mean BMI was 22 kg/m2 (mean BMI percentile = 77th), and 41 % were overweight (BMI ≥ 95th percentile using CDC 2000 growth charts). Participants' intake of fruits and vegetables (1.3 serving/day) and fats (36 % kcal), and their participation in moderate-to-vigorous physical activity (20 min/day), did not meet national recommendations. The GEMS obesity prevention intervention targets improved diet and increased physical activity to reduce excessive weight gain in healthy African-American girls of ages 8–10.