The effect of hydraulic circuit training (HCT) on stroke volume (SV), cardiac output (Qc), aerobic power (peak VO2), and muscular strength and endurance was evaluated in 24 post-coronary artery bypass (CABS) patients (mean age = 52.8 +/- 2.6 yr). All assessments other than muscular strength and endurance were based upon a symptom limited graded exercise test on a bicycle ergometer. Muscular strength and endurance were assessed on a Cybex II isokinetic dynamometer. Sixteen patients were assigned randomly to 8 wk of cycle training or HCT (N = 8 in each). Subjects assigned to cycle training exercised on bicycle ergometers. The HCT group exercised on a three-station circuit, completing three circuits per day. Each circuit consisted of three 20 s work intervals at each station with a 1:1 work:rest ratio. Results from the training groups were compared with results from eight patients who served as a nonexercising control group. Following training the peak VO2 was significantly increased in the training groups (20% and 11% for the cycle and HCT groups, respectively; P less than 0.05). For both training groups, the increase in peak VO2 was associated with increases in SV and Qc and a reduction in heart rate (HR) at submaximal levels of exercise (P less than 0.05). Only the HCT group demonstrated an increase in both muscular strength and endurance during knee and shoulder exercises (P less than 0.05). These findings suggest that a program of HCT can elicit improvements in cardiovascular fitness and muscular strength and endurance in post-CABS patients.