Objective To evaluate the effects of Carvedilol on cardiopulmonary bypass (CPB)-induced myocardiocyte apoptosis and its effect on regulation of Fas, FasL expression, caspase-3 activity and oxidative stress in the left ventricle (LV) in this setting.Methods Ten adult dogs undergoing conventional hypothermic CPB were randomly divided into control and Carvedilol treated groups (n=5, respectively). Dogs in Carvedilol treated group 3 μg*min-1*kg-1 received a bolus of Carvedilol (1 mg/kg) intravenously and a maintenance dosage of Carvedilol for 3 hours after the reperfusion of the heart. Dogs in control group received no carvediolol. LV samples were obtained before, during and 3 hours after CPB. In situ nick end-labeling (TUNEL) technique was used to detect the apoptotic cells. The expressions of Fas and FasL were detected immunohistochemically and quantified by fluorescence activated cell sorting (FACS). The activity of caspase-3 enzyme and malondialdehyde (MDA) level were measured by cleavage of Z-DEVD-AMC substrate and thiobarbituric acid reactive substances (TBARS) method, respectively. Results Before and during CPB, all the parameters were not significantly different between groups (P>0.05). After CPB, these parameters in both groups were significantly elevated compared with those of before and during CPB (P<0.028, respectively). However, the number of apoptotic cells in Carvedilol treated group was significantly decreased compared with that of the control group (P<0.021). The expressions of Fas and FasL were significantly downregulated by Carvedilol (P<0.001 and 0.003, respectively). The caspase-3 activity and the content of MDA in the Carvedilol treated group was also significantly reduced (P<0.026 and 0.005, respectively). Conclusions Carvedilol significantly reduces CPB-induced cardiomyocyte apoptosis in dog hearts and the reduction of cardiomyocyte apoptosis is associated with downregulation of Fas and FasL expression, inhibition of caspase-3 activity and oxidative stress in LV.