Anthropometric and demographic characteristics are important determinants of exercise performance in healthy subjects, but their influence has not yet been studied in severe chronic heart failure, although peak oxygen uptake is frequently assessed in such patients for prognostic purposes. The aim of the present analysis was to examine the association between peak oxygen uptake and age, gender, and measures of body size in patients with severe chronic heart failure. We selected 122 (99 male) adult heart transplant candidates who were able to perform a bicycle ergometer test with respiratory gas analysis until voluntary fatigue. Peak oxygen uptake was higher in male than in female patients, both before and after adjustment for weight. In single regression analysis on the total study population, peak oxygen uptake was positively related to weight and to height, but inversely to age (r = 0.59 (P< 0.001), 0.42 (P < 0.001), and -0.33 (P < 0.001), respectively). Multiple stepwise regression analysis identified weight(P < 0.001), age (P < 0.001), and gender(P < 0.01) as independent determinants of peak oxygen uptake(cumulative R2 = 0.45). Similar to the findings in healthy subjects, peak oxygen uptake of patients with severe chronic heart failure is influenced by anthropometric and demographic characteristics.