Graft rejection is characterized by cellular infiltration, reduction in blood flow, and intravascular coagulation, finally resulting in graft failure and absolute increase in thromboxane and relative decrease in prostacyclin synthesis. It is also suspected that prostaglandin itself could cause prolongation of allograft survival. In this experimental study, after successful heterotopic cardiac transplantation in rats, CyA was administered by intramuscular injection and prostaglandin E1 (PGE1) given into the peritoneal cavity. Each dose was according to the experimental designs. The authors found that PGE1 in addition to CyA could provide beneficial effects with significantly increased cardiac allograft survival, with amelioration of pathological changes in allograft rejection reaction.