Background: Video games designed to promote behavior change are a promising venue to enable children to learn healthier behaviors. Purpose: Evaluate outcome from playing "Escape from Diab" (Diab) and "Nanoswarm: Invasion from Inner Space" (Nano) video games on children's diet, physical activity, and adiposity. Design: Two-group RCT; assessments occurred at baseline, immediately after Diab, immediately after Nano, and 2 months later. Data were collected in 2008-2009, and analyses were conducted in 2009-2010. Setting/participants: 133 children aged 10-12 years, initially between 50th percentile and 95th percentile BMI. Intervention: Treatment group played Diab and Nano in sequence. Control Group played diet and physical activity knowledge-based games on popular websites. Main outcome measures: Servings of fruit, vegetable, and water; minutes of moderate to vigorous physical activity. At each point of assessment: 3 nonconsecutive days of 24-hour dietary recalls; 5 consecutive days of physical activity using accelerometers; and assessment of height, weight, waist circumference, and triceps skinfold. Results: A repeated measures ANCOVA was conducted (analyzed in 2009-2010). Children playing these video games increased fruit and vegetable consumption by about 0.67 servings per day (p < 0.018) but not water and moderate-to-vigorous physical activity, or body composition. Conclusions: Playing Diab and Nano resulted in an increase in fruit and vegetable intake. Research is needed on the optimal design of video game components to maximize change. (Am J Prev Med 2011; 40(1): 33-38) (C) 2011 American Journal of Preventive Medicine