Cyclosporine A (CsA) has been shown to protect against myocardial ischemia and reperfusion (I/R) injury in small animal models. The aim of the current study was to evaluate the effects of CsA on myocardial I/R injury in a porcine model. Pigs were randomized between CsA (10mg/kg; n = 12) or placebo (n = 15) and anesthetized with either isoflurane (phase I) or pentobarbital (phase II). By catheterization, the left descending coronary artery was occluded for 45 minutes, followed by reperfusion for 2 hours. Hearts were stained to quantify area at risk (AAR) and infarct size (IS). Myocardial biopsies were obtained for terminal dUTP nick end labeling and immunoblot analysis of proapoptotic proteins (apoptosis-inducing factor [AIF], BCL2/adenovirus E1B 19-kd interacting protein 3 [BNIP-3], and active caspase-3). Cyclosporine A did not reduce IS/AAR compared with placebo (49% vs 41%, respectively; P = .21). Pigs anesthetized with isoflurane had lower IS/AAR than pigs anesthetized with pentobarbital (39% vs 51%, respectively; P = .03). This reduction in IS/AAR seemed to be attenuated by CsA. Apoptosis-inducing factor protein expression was higher after CsA administration than after placebo (P = .02). Thus, CsA did not protect against I/R injury in this porcine model. The data suggest a possible deleterious interaction of CsA and isoflurane.