To assess the compensatory change in oxygen uptake (VO₂) kinetics during exercise in patients with heart failure, we performed cardiopulmonary exercise testing using a cycle ergometer in 29 cardiac patients and 18 normal subjects. The work rate increased linearly (1w/6sec) after a 4 min, 20w warm-up. The ratio of increase in VO₂ to increase in work rate (ΔVO₂/Δ WR) was determined by linear regression of VO₂ plots. Cardiac output by dye dilution method and plasma norepinephrine concentration (NE) were measured at rest and 20w warm-up. VO₂ at rest and at 20w warm-up and ΔVO₂/ΔWR decreased significantly with increasing severity in NYHA functional classification. ΔVO₂/ΔWR showed significant negative correlation to the difference in NE levels at rest and at 20w (r=-0.69, p<0.001). The delta values of arteriovenous O₂ content difference, calculated using Fick's principle, and cardiac index from rest to 20w warm-up failed to show significant relationship to ΔVO₂/ΔWR. These results suggest that the decrease in VO₂ requirement in heart failure patients is due probably to blood redistribution during exercise as a compensatory mechanism for exercise intolerance.