415 preschool boys and 368 girls in Belgium were observed and wore pedometers during recess. Boys took significantly more steps per minute than girls (65 versus 54 steps/min). In both genders higher step counts per minute were significantly associated with less children per m2 and with shorter recess times. In girls higher step counts were associated with the presence of less supervising teachers. Playground markings, access to toys, the number of playing or aiming equipment pieces and the presence of vegetation or height differences were not significant physical activity predictors in both genders.