OBJECTIVE: To observe the effect and safety of cardiac rehabilitation (CR) exercise in ischemic cardiomyopathy and to compare the results between patients with preserved left ventricular ejection fraction (LVEF) and reduced LVEF. METHODS: Patients with ischemic cardiomyopathy with LVEF <50% were included as subjects. The patients were classified into the preserved LVEF (pLVEF; LVEF 41%–49%) group and the reduced LVEF (rLVEF; LVEF ≤40%) group. Patients underwent hourly aerobic exercise training sessions with an intensity of 60%–85% of heart rate reserve, three times a week for 6 weeks. Graded exercise test and transthoracic echocardiogram were performed in all study patients before and after completion of the CR exercise program. RESULTS: After completion of the CR exercise program, both groups (pLVEF, n=30; rLVEF, n=18) showed significant increases in LVEF and VO(2max). In the pLVEF group, LVEF and VO(2max) increased from 45.1%±4.8% to 52.5%±9.6% (p<0.001) and from 24.1±6.3 to 28.1±8.8 mL/kg/min (p=0.002), respectively. In the rLVEF group, LVEF and VO(2max) increased from 29.7%±7.7% to 37.6%±10.3% (p<0.001) and from 17.6±4.7 to 21.2±5.1 mL/kg/min (p<0.001), respectively. Both groups completed their exercise program safely. CONCLUSION: In both groups, patients with ischemic cardiomyopathy who completed a 6-week supervised CR exercise program demonstrated remarkable improvements in cardiopulmonary function. This result implies that neither of the two groups showed higher efficacy in comparison to each other, but we can conclude that CR exercise in the rLVEF group was as effective and safe as that in the pLVEF group.