While cyclosporine immunosuppression has improved the results of heart transplantation, nephrotoxicity and hypertension occurred in a large percentage of surviving patients. The potential irreversibility of these toxicities was noted in patients chronically exposed to cyclosporine. The immunosuppressive protocol was modified in those patients with a serum creatinine greater than 2.5 mg/100 mL. Azathioprine was added to the immunosuppressive regimen, and the dose of cyclosporine was steadily decreased until the creatinine was lowered. The combination of low-dose cyclosporine and azathioprine provided effective immunosuppression and was associated with a significant decrease in serum creatinine level, in systolic and diastolic blood pressures. Although it is premature to assess the long-term results of this immunosuppressive protocol, the early results are encouraging.