Objectives: This study was conducted to determine the effects of carvedilol adjunct to standard treatment on left ventricular function (LVF), estimated as election fraction (EF) and fractional shortening (FS) on echocardiography, in children with idiopathic dilated cardiomyopathy (DCM). A secondary end point was to characterize the antioxidant potential of carvedilol. Methods: Hospitalized children aged 62.5 kg) was associated with significant decreases from baseline in systolic BP (130 [4] vs 123 [3] mm Hg; P < 0.05), diastolic BP (85 [4] vs 77 [4] mm Hg; P < 0.05), and HR (81 [4] vs 65 [4] bpm; P < 0.001) after the first month of addition to standard therapy. At 6 months, there were significant improvements from baseline in EF (37.2% [2.4%] vs 50.2% [2.3%]; P < 0.001) and FS (18.37% [2.00%] vs 23.58% [0.90%]; P < 0.001). Modified NYHAC class was significantly improved in 80% of children (2.9 vs 2.3; P < 0.001) at 12 months. The highest dose of carvedilol (0.8 mg/kg/d in children: 62.5 kg or 50 mg/d in children > 62.5 kg) was well tolerated in all 21 children. No serious AEs that necessitated study drug discontinuation (tiredness, headache, vomiting) were observed. At baseline, mean (SE) erythrocyte SOD activity (2781 [116] vs 2406 [102] U/g Hb; P < 0.05) and GR activity (5.3 [0.3] vs 3.0 [0.2] mu mol nicotinamide adenine dinucleotide phosphate [NADPH]/min/g Hb; P < 0.001) were significantly higher in children with DCM who received standard therapy compared with healthy controls. CAT activity (12.7 [0.9] vs 18.5 [1.0] U/g Hb; P < 0.001) was significantly lower, while GSH-Px was unchanged. At 6 and 12 months of therapy, carvedilol plus standard treatment was associated with significant decreases from baseline in SOD (2516 [126] and 2550 [118], respectively, vs 2781 [116] U/g Hb; both, P < 0.001) and GR (4.7 [0.3] and 4.1 [0.2], respectively, vs 5.3 [0.2] mu mol NADPH/min/g Hb; P < 0.05 and P < 0.001) and increased CAT (16.9 [1.0] and 16.4 [0.7], respectively, vs 12.7 [0.9] U/g Hb; both, P < 0.001). Conclusions: These pediatric patients with DCM treated for 12 months with carvedilol (up to 0.8 mg/kg/d in children: 62.5 kg or 50 mg/d in children > 62.5 kg) were found to have significant improvements in LVF and symptoms of HE Twelve months of carvedilol therapy was associated with antioxidant enzyme activities near those observed in healthy children. null