We evaluated the effect of glutathione (YM737) as a free radical scavenger, when added to hypothermic ( 4℃ ) crystalloid cardioplegic solution (K^+23mmol/l). Rabbit hearts were preserved for 3 hours in cardioplegic arrest by infusing 20 ml initially, with additional 10 ml boluses administered every 30 minutes. The myocardial temperature was maintained at 10℃. The hearts were reperfused with KHBB 37℃ in a per fusion circuit for 60 minutes. The animals were divided into two groups. In group I (n=6), crystalloid cardioplegic solution was per fused. In group II(n=6), crystalloid cardioplegic solution containing glutathione (YM737