The ability of nifedipine to enhance myocardial protection was assessed on isolated perfused rat hearts subjected to 180 min of hypothermic (20°C), global ischemia, followed by 45 min of normothermic reperfusion. Intracellular pH, ATP, pi and phosphocreatine content were serially measured at 4 min intervals by phosphorus-31 nuclear magnetic resonance spectroscopy and correlated with simultaneously recorded hemodynamic parameters. Addition of nifedipine (0.075 μmol/l and 0.5 μmol/l) to Saint Thomas' cardioplegic solution reduced Pi accumulation during ischemic arrest and increased phosphocreatine levels during reperfusion. Post-ischemic functional recovery was not improved at a drug concentration of 0.075 μmol/l and was depressed at 0.5 μmol/l. These results clearly show that the presence of nifedipine in Saint Thomas' cardioplegic solution does not provide significant additional myocardial protection under hypothermic conditions. © 1985.