We have studied a standardized exercise protocol suitable for use with a treadmill or bicycle (STEEP protocol) and compared it with a modified Bruce treadmill protocol in a group of patients with chronic cardiac failure. The STEEP protocol has been previously validated in normal subjects. Exercise time (6.79 +/- 2.42 vs 5.34 +/- 1.95 min, P < 0.05) and peak VO2 (16.66 +/- 4.09 vs 15.01 +/- 3.72 ml.min-1.kg-1, P < 0.05) were greater with the STEEP treadmill compared with the bicycle protocol, but VO2 was very similar at equal exercise stages in both modalities. Heart rate and respiratory exchange ratio tended to be greater during bicycle exercise at equal stages. Exercise time was greater with the modified Bruce protocol (9.00 +/- 3.02 min, P < 0.05) than with either STEEP protocol, but peak VO2 (17.13 +/- 4.52 ml.min-1.kg-1) was similar to that obtained with the STEEP treadmill test. We conclude that the STEEP protocol may be used to test patients with chronic cardiac failure, and that exercise times relate well in both treadmill and bicycle. The protocol should prove useful in studies involving a wide range of exercise capacities or both bicycle and treadmill exercise.