The purpose of this study was to compare metabolic responses between men and women during water walking. Japanese men (27-73 yr, n = 26) and women (33-70 yr, n = 14) performed water walking at 25 m/min, 30 m/min and 35 m/min. Oxygen consumption (VO2), VO2 per weight (VO2/W), respiratory ventilation (VE), heart rate (HR), energy expenditure (EE), EE per weight (EE/W), and actual walking speed were analyzed at each velocity. VO2/W and EE/W were higher in women compared to men. However, VO2 and EE showed similar values between men and women. HRs were significantly higher for women than those of men at all speeds. The regression analysis with third-ordered polynomial equation by actual walking speed showed high correlation coefficients for VO2 and VO2/W. In relative terms exercise intensity was higher for women than men; however, absolute intensity were similar in both men and women during water walking. Moreover, analysis using third-ordered equations found that absolute intensity during water walking was dominated by walking speed