Heterotopic cardiac transplantation is a useful method for studying allograft rejection. In this study a new technique of cardiac transplantation was carried out, which involved retroperitoneal anastomoses of the donor ascending aorta and main pulmonary artery with the recipient abdominal aorta and inferior vena cava respectively. The procedure was simple and effective and was accomplished with minimal operative mortality and postoperative morbidity. The method allows better access to the allograft for repeated open myocardial biopsies, obviating the limitations of transvenous fluoroscopically directed endomyocardial biopsy. This technique of retroperitoneal heterotopic cardiac transplantation has important advantages compared with similar procedures performed in the neck, abdomen, or thorax.