Abstract: AIM:To investigate the effects of sevoflurane on immature myocardial protection and scavenging of oxygen free radicals (OFRS). METHODS: Sixty patients undergoing surgery for congenital heart diseases (ages 2 to 9 years; ASA grade II or III) were randomly divided into sevoflurane group (sev group, n=30) and propofol group (pro group, n=30) during induction of anesthesia. Sev group inhaled oxygen for 5-6 L/min+40-60 ml/L sevoflurane and pro group for propofol 1-2 mg/kg. Both groups were given midazolam 0.05-0.1 mg/kg, vecuronium 0.1 mg/kg, and sufentanil 1 μg/kg. In sev group, anesthesia was maintained with inhalation of sevoflurane, 4-8 ml/L, and in pro group with propofol 1-3 mg/(kg·h). Anesthesia in both groups was maintained with vecuronium 0.1 mg/(kg·h) and sufentanil 30-40 μg/kg. Before induction of anesthesia (T0), at the beginning of cardiopulmonary bypass (T1) and at the end of cardiopulmonary bypass (T2), and at the end of operation (T3), plasma malondialdehyde (MDA) and superoxide dismutase enzyme (SOD) from blood were detected. RESULTS: No obvious difference in MDA and SOD was observed between groups at T0 and T1 (P>0.05), but in sev group, SOD was significantly higher and MDA was significantly lower at T2 and T3 (both P<0.05). CONCLUSION: Sevoflurane is superior to propofol in protection of immature myocardia, possibly via reduced reaction of the oxidative stress by scavenging oxygen free radicals.