['To assess whether the underlying aetiology of chronic heart failure is a predictor of exercise performance.', 'Tertiary referral centre for cardiology.', 'Retrospective study of maximum exercise testing with metabolic gas exchange measurements in 212 patients with chronic heart failure who had undergone coronary angiography. Echocardiography and radionucleide ventriculography were used to determine indices of left ventricular function, and coronary arteriography was used to determine whether the cause of chronic heart failure was ischaemic heart disease (n = 122) or dilated cardiomyopathy (n = 90).', 'The cardiomyopathy group was younger (mean (SD) age 58.45 (11.66) years v 61.49 (7.42); p = 0.02) but there was no difference between the groups in ejection fraction or fractional shortening. Peak oxygen consumption (VO2) was higher in the dilated group, while the slope relating carbon dioxide production and ventilation (VE/VCO2 slope) was the same in both groups. Both groups achieved similar respiratory exchange ratios at peak exercise, suggesting that there was near maximum exertion. There was a relation between peak VO2 and age (peak VO2 = 33.9-0.267*age; r = 0.36; p < 0.001). After correcting for age, the peak achieved VO2 was still greater in the cardiomyopathy group than in the ischaemic group (p < 0.002).'] Is exercise capacity in chronic heart failure related to the aetiology of heart disease?