The purpose of this study was to investigate whether differences exist between boys and girls in submaximal cardiovascular responses to exercise on both the treadmill and cycle ergometer. Twenty-four (12 boys and 12 girls) 7- to 9-yr-old children participated in two maximal (one treadmill and one cycle) and four submaximal tests (two treadmill and two cycle). There were no significant differences between the boys and girls in maximal oxygen consumption (L.min-1 or mL.kg-1.min-1) or physical characteristics except for a significantly larger left ventricular mass in the boys versus the girls (78.8 vs 66.0 g, respectively). Submaximal cardiovascular variables were measured at three different work rates on both exercise modalities. Oxygen consumption at the different work rates was not different between boys and girls on either exercise modality. The trend was for heart rate to be lower and stroke volume higher in boys versus girls, but this difference was only significant for heart rate at 4 miles.h-1 (142.9 vs 155.5 beats.min-1, respectively). It is concluded that in this sample of 7- to 9-yr-old boys and girls there are few significant differences in submaximal cardiovascular responses to exercise on either exercise modality.