In order to assess possible influences of socioeconomic status and gender on habitual physical activity (HPA) of prepubertal French children, daily heart rate was 24-hr-monitored in 65 normal subjects for 2 days in the same school week. HPA was evaluated as the mean daily time spent at heart rates greater than 140 bpm (tFC > 140), 160 bpm (tF C > 160), 50% (tFC > 50%), and 70% (tFC > 70%) of the heart rate reserve. An effect of socioeconomic status (determined by questionnaire) was found in boys, with HPA being greater in the underprivileged ones (tFC > 140: 51.8 +/- 30.1 vs 33.0 +/- 14.1 min, p < .05; tFC > 160: 22.7 +/- 16.6 vs 11.1 +/- 7.4 min, p < .05; tFC > 50%: 61.4 +/- 33.5 vs 46.5 +/- 17.1 min, p < .06; tFC > 70%: 20.1 +/- 15.2 vs 10.6 +/- 7.1, p < .05). Boys were more active than girls, but only in the underprivileged group (tFC > 140: 51.8 +/- 30.1 vs 32.8 +/- 26.0 min, tFC > 160: 22.7 +/- 16.6 vs 9.9 +/- 8.2 min, p < .05; tFC > 50%: 61.4 +/- 33.5 vs 37.4 +/- 23.8 min, p < .05; tFC > 70%: 20.1 +/- 15.2 vs 8.1 +/- 6.3, p < .05). Cultural factors could be involved in these results.