The purpose of this study was to compare the physiological responses to water walking with water temperature of 30℃ versus land walking with room temperature of 25℃ at the same oxygen up-take level to obtain useful data that could eventually be applied to instruction in water walking. Eight healthy, male college students (19±1.0yr, 168.2±3.7cm, 60.8±4.6kg) volunteered to participate in this study. Each subject walked on a treadmill set on land and in water, at 50% of maximal aerobic power for 1 hour, respectively. During tests in the water, subjects were immersed to a level of the xiphisternal. The oxygen uptake (VO_2), heart rate (HR) and rectal temperature (RT) were all measured continuously during both types of walking. Blood samples were collected before walking, and then every 10min while walking to analyze the plasma lactate concentration (LA). Samples for plasma adrenaline (AD) and noradrenaline (NAd) concentration were measured before walking, and at 30 and 60min while walking. There were no differences in VO_2 and LA between the water and land walking throughout the 60min of exercise. The HR and RT in water walking were lower than those for land walking, and the differences in these parameters between the water walking and land walking increased over time. The plasma NAd concentration during water walking was significantly lower than that in the land walking, whereas the plasma AD concentration did not differ significantly in either type of walking. During water walking, plasma NAd concentration at 30min did not differ significantly from at rest, but that of at 60min increased significantly from at rest. These results show that water walking with water temperature of 30℃ induced lower HR and sympathetic nervous activity than that observed on land with room temperature of 25℃ at similar levels of VO_2. Water walking in this study may be a useful training mode of cardiovascular rehabilitation programs. It is also, suggested that the heart rate during water walking seemed to be a suitable means of monitoring prolonged exercise intensity, and that sympathetic nervous activity would increase in the latter of the prolonged water walking, but its elevation is smaller than that obsered during land walking.