OBJECTIVE: To examine the effect and safety of cardiac rehabilitation (CR) program in high-risk cardiac patients and compare these results to those of control CR participants without high-risk criteria. METHODS: A total of 12 high-risk cardiac patients were recruited as subjects. The high-risk criteria were: advanced heart failure with left ventricular ejection fraction (LVEF) of less than 30%, a recent history of cardiac arrest or dangerous arrhythmia, and cardiac device insertion. Another 12 CR participants without any high-risk criteria mentioned above were recruited as controls. Both groups underwent 6 to 8 weeks of CR exercise training. Exercise tolerance tests were performed before and after completion of the CR program. After CR completion, both groups were evaluated and their results were compared. RESULTS: After completion of the CR exercise program, both groups showed significant increases in peak oxygen uptake (VO(2peak)) and LVEF. In the control group (n=12), VO(2peak) increased from 25.9 to 31.8 mL/kg/min (changing rate, +21.4%±22.1%) and LVEF increased from 56.1% to 59.1% (changing rate, +5.3%±8.4%). In the high-risk group (n=12), VO(2peak) increased from 16.8 to 21.0 mL/kg/min (changing rate, +28.6%±21.4%) and LVEF increased from 26.1% to 29.4% (changing rate, +16.1%±12.9%). There was no serious cardiovascular event during all exercise hours. CONCLUSION: High-risk cardiac patients who completed a supervised CR program demonstrated significant improvements in VO(2peak) and LVEF without any serious cardiovascular event. The improvement rate was similar to that of control group.