To measure the energy expenditure and enjoyment of children's games to be used in developing a school-based intervention for preventing excessive weight gain.Healthy weight (body mass index [BMI] <85 th percentile) and overweight or obese (BMI ≥85 th percentile) third-grade children (15 boys; 13 girls) were recruited. In a large gymnasium, children performed 10 games randomly selected from 30 games used in previous interventions. Total energy expenditure was measured with a portable metabolic unit and perceived enjoyment was assessed using a 9-point Likert scale of facial expressions. Mean physical activity energy expenditure (PAEE = total energy expenditure minus resting metabolism) and enjoyment of the games were adjusted for sex and BMI classification. PAEE and enjoyment were compared using a repeated-measures ANOVA with sex, BMI classification, and games as main effects.The games elicited a moderate intensity effort (mean ± standard deviation = 5.0 ±1.3 metabolic equivalents, 123 ±36 kcal/30 min). PAEE was higher for boys than for girls (0.12 ±0.04 versus 0.11 ±0.04 kcal/kg/min) and for healthy weight compared with overweight children (0.13 ±0.04 versus 0.11 ±0.03 kcal/kg/min). Twenty-two of the 30 games elicited a sufficiently high PAEE (≥100 kcal/30 min) and enjoyment (≥ neutral expression) for inclusion in future school-based interventions.Not all children's games are perceived as enjoyable or resulted in an energy expenditure that was sufficiently high for inclusion in future physical activity interventions to prevent the excess weight gain associated with childhood obesity.