The purpose of this study was to investigate the maximum limits of a simple topical cooling method with preservation of graft viability following orthotopic transplantation. Coronary vascular washout was performed with cold potassium-verapamil cardioplegia. The heart was then removed, suspended in the same solution, and stored at 4 degrees C. The experimental material was divided into three groups according to the preservation time: 24 h in group I (six animals), 36 h in group II (five animals), and 48 h in group III (three animals). All six animals in group I and four of five animals in group II maintained a stable recipient circulation after transplantation. No animals in group III could be taken off cardiopulmonary bypass. Contraction band injury after transplantation was more frequently observed in the group II grafts than in those of group I. In conclusion, the combination of coronary vascular washout with cold potassium-verapamil cardioplegia and storage at 4 degrees C in the same solution may preserve the canine heart for 24-36 h, as demonstrated by cardiac function immediately after orthotopic transplantation.