Several different exercise testings with treadmill, bicycle ergometer and two-step were carried out by healthy Japanese men to study oxygen consumption per minute and circulatory responses. Stress imposed on the heart by dynamic leg exercise varied depending on the mode of exercise even if energy expenditure expressed in V^^·O₂ was identical. This should be fully taken into consideration in comparison of results of different modes of exercise testings. For estimation of V^^·O₂ during treadmill slope walk, an equation was derived by multiple regression analysis with use of belt speed and slope as independent variables.