In this study we investigated the factors influencing the development of hypertension in 488 consecutive heart transplant recipients. The cumulative probability of hypertension (blood pressure persistently above 150/95 mm Hg) developing was 52% at 1 year, 67% at 2 years, 73% at 3 years, and 77% at 4 years after transplantation. The incidence was higher in patients receiving cyclosporine and azathioprine compared with those receiving prednisone and azathioprine immunosuppression. The dose of cyclosporine used did not appear to influence the development of hypertension. Intermittent steroid exposure did not increase the incidence in the cyclosporine group. Male transplant recipients and those older than 20 years appeared more prone to the development of hypertension. A family history of cardiovascular disease also increased the incidence. Preoperative and postoperative kidney dysfunction and transplantation because of ischemic heart disease did not appear to affect the incidence of hypertension. Donor characteristics, including the use of hearts from donors who weighed more than the recipients and from patients dying of spontaneous intracranial hemorrhage, did not appear to increase the incidence of hypertension after heart transplantation.