Background Peak exercise oxygen consumption (peak VO₂) is an important discriminator of survival in patients with systolic heart failure and is used to select ambulatory patients for transplantation. The major trials assessing the relationship between peak VO₂ and survival have used a variety of low-level exercise protocols. It is unknown how peak VO₂ measured in this patient population by the more vigorous Bruce treadmill protocol compares with that obtained on less intense protocols. Methods We studied 15 patients (50 ± 12 years old) with severe heart failure (left ventricular ejection fraction 23.5% ± 8.6%). Patients randomly performed 3 exercise tests with the Bruce treadmill, modified Naughton treadmill, and modified bicycle protocols within 14 days. To determine the ability of this patient population to perform the Bruce protocol, we also retrospectively analyzed the ability of 84 patients to perform this test on their initial evaluations at our center. Results All patients reached the anaerobic threshold (AT) on all 3 protocols. The Bruce and modified Naughton treadmill protocols resulted in similar peak VO_2, percent predicted peak VO₂, and VO₂ at AT values (17.7 ± 3.8 mL/kg/min, 57.2% ± 21.1% and 15.4 ± 4.1 mL/kg/min vs 18.0 ± 4.7 mL/kg/min, 58.1% ± 22.5% and 15.6 ± 4.4 mL/kg/min, respectively). Peak VO₂ and VO₂ at AT on both treadmill protocols were higher than those obtained with bicycle testing (15.3 ± 3.1 and 11.8 ± 3.0 mL/kg/min, P <.05). Exercise duration was shorter with the Bruce and bicycle protocols (6.2 ± 2.2 and 6.7 ± 2.4 minutes, respectively) compared with the modified Naughton protocol (9.7 ± 4.3 minutes, both P <.005). In addition, 79 of the 84 patients (94%) evaluated were able to complete the Bruce protocol and reach AT. Conclusions The Bruce protocol was more time efficient than the modified Naughton protocol and yielded similar peak VO₂, percent predicted peak VO₂, and VO₂ at AT values. Bicycle exercise may underestimate peak VO₂ values. The form of exercise should be considered when assessing peak VO₂ criteria for transplant listing. (Am Heart J 2001;142:466-75.)