Background—The effects of exercise training (ET) on left ventricular (LV) remodeling in chronic heart failure are not definitively established, and the safety of ET in these patients is still debated.Methods and Results—This multicenter study investigated the long-term effect of moderate ET on LV remodeling, work capacity, and quality of life (QoL) in 90 patients with stable chronic heart failure caused by LV systolic dysfunction, randomized to a 6-month ET program (T, n=45) or a control group (C, n=45). All patients underwent resting echocardiography, a cardiopulmonary exercise test, 6-minute walking test, and QoL assessment at entry and after 6 months. At entry, end-diastolic (EDV) and end-systolic (ESV) volume, ejection fraction, work capacity, peak &OV0312;o2, and walking distance were similar in the 2 groups. After 6 months, LV volumes diminished in T (EDV, from 142±26 to 135±26 mL/m2,P<0.006; ESV, from 107±24 to 97±24 mL/m2,P<0.05) but increased in C (EDV, from 147±41 to 156±42 mL/m2,P<0.01; ESV, from 110±34 to 118±34 mL/m2,P<0.01). Ejection fraction improved in T (P<0.001) but was unchanged in C (P=NS). Significant improvement in work capacity (P<0.001), peak &OV0312;o2(P<0.006), walking distance (P<0.001), and QoL (P<0.01) was observed in T but not in C (P=NS). T showed a trend toward fewer (P=0.05) hospital readmissions for worsening dyspnea in the absence of other adverse cardiac events.Conclusions—In stable chronic heart failure, long-term moderate ET has no detrimental effect on LV volumes and function; rather, it attenuates abnormal remodeling. Furthermore, ET is safe and effective in improving exercise tolerance and QoL.