Two studies were conducted to examine the interactions between gender, play area, motor skills and free play activity in 8-11 year old school children. In both studies, boys were more active than girls. In boys, but not in girls, energy expenditure was greater for high-skill than for low-skill children (p = 0.0002), and increased as play area increased (p = 0.01). These results suggest that motor skills and play space are important variables in determining the free play activity of boys, but not of girls. This may be related to widely different play styles among boys and girls.