The effects of training as part of a comprehensive rehabilitation programme on exercise capacity and habits was studied in 171 male coronary artery bypass surgery patients randomized into a rehabilitation (R) (n = 93) and a reference, hospital-based treatment (H), group (n = 78). The rehabilitation programme started with a 2-day informative course before surgery and continued with a 3-week exercise-based course 2 months after surgery followed by a 2-day refresher 8 months post-operatively. The percentages of subjects having regular exercise were 22% and 10% pre-operatively, 42% and 38% 6 months and 46% and 38% 12 months after surgery in the R and H groups, respectively. The changes in the proportions observed in R and H groups were not significantly different. Total work during a bicycle exercise test increased from 38.9 +/- 24.3 kJ pre-operatively to 64.0 +/- 31.4 kJ 6 months (P less than 0.001) and to 70.0 +/- 35.7 kJ 12 months (P less than 0.001) post-operatively in group R and from 40.8 +/- 25.6 kJ to 57.3 +/- 26.6 kJ (P less than 0.001) and to 60.4 +/- 30.8 kJ (P less than 0.001) in group H, respectively. The increase from the pre-operative value was greater in group R than in group H both 6 (P = 0.03) and 12 months (P = 0.02) after surgery. Respective changes occurred in maximal work load, but the increase was significantly greater in group R than in group H only 12 months post-operatively.(ABSTRACT TRUNCATED AT 250 WORDS)