In patients with severe congestive heart failure, a marked elevation in pulmonary vascular resistance limits the success of orthotopic cardiac transplantation, thus providing the rationale for heterotopic transplantation. To determine the changes in pulmonary hemodynamics after heterotopic cardiac transplantation, postoperative right heart pressures were serially measured in five patients who underwent this operation for end-stage congestive heart failure accompanied by severe secondary pulmonary hypertension and elevation in calculated pulmonary vascular resistance. Hemodynamics were compared with those of a matched group of 10 orthotopic cardiac transplant recipients. Preoperatively, pulmonary artery mean and wedge pressures, pulmonary vascular resistance and transpulmonary pressure gradient (pulmonary artery mean minus wedge pressure) were significantly higher in the heterotopic group. Postoperatively, significant improvement in pulmonary hemodynamics occurred in both groups and, by 12 months, the pulmonary artery mean pressure, wedge pressure, pulmonary vascular resistance and transpulmonary pressure gradient were similar in the two groups. These findings suggest that pulmonary hypertension secondary to congestive heart failure, even when severe and associated with a high pulmonary vascular resistance, is to a great extent reversible.