The purpose of this study was to investigate the effect of postural position on oxygen uptake, heart rate, and ventilation during submaximal and maximal work by use of a bicycle ergometer. Ten healthy male subjects, aged 19-33 years, performed submaximal and maximal tests on a bicycle ergometer in three different body positions. The postural positions during exercise used in this study were sitting (S) position, the horizontal supine (H) position, and the supine position with legs elevated to 45° (E). Each subject performed 5-min submaximal tests of three different intensities and maximal tests with stepwise incremental loading in each body position. In submaximal tests, no significant differences were observed in oxygen uptake and heart rate at a given work load among S-, H-, and E-positions. The average values of maximal oxygen uptake obtained in H- and E-positions were corresponded to 95.5% and 87.6% of maximal oxygen uptake in S-position, respectively. Maximal heart rate in H- and E-positions were 2.4% and 6.5% lower compared to cycling in S-position, respectively. On these values, the statistically significant differences were found between S- and E-positions and between H- and E-positions (p < 0.05-0.001). Total work performed until exhaustion in H- and E-positions was equivalent to 64.9% and 58.3% of total work in S-position, respectively. Statistically significant differences were observed among these three positions (p < 0.01-0.001).