The ideal combination of immunosuppressants after heart transplantation that safely prevents graft rejection and maintains a low rate of infections and toxic side effects is still a topic of discussion. Between March 1984 and March 1988, 76 patients underwent orthotopic heart transplantation. Sixty-five patients received either double-drug (cyclosporine + azathioprine) or triple-drug (cyclosporine + azathioprine + steroids) maintenance therapy. In addition all patients with double-drug protocol (group 1, n = 13) and the majority with triple-drug protocol (group 2, n = 39) received prophylactic antithymocyte globulin (ATG); 13 patients with triple-drug protocol (group 3) received prophylactic monoclonal antibody (murine antihuman mature T cell [OKT3]). Recipients with perioperative or intraoperative deaths, maintenance protocol without cyclosporine, or previous total artificial heart bridge were excluded from the study. Cyclosporine was given in low doses according to a trough whole blood high-performance liquid chromatography target level of 200 to 400 ng/ml in the first month, 150 to 250 ng/ml from the second to sixth month, and 100 to 150 ng/ml after the sixth month. Azathioprine dose was adjusted to a leukocyte count of approximately 4,000 cells/mm3. In patients with triple-drug protocol, prednisolone (0.2 mg/kg/day) was added. The mean follow-up (group 1, 12.75 months; group 2, 12.84 months) was comparable between the groups who received ATG perioperatively. The mean follow-up for group 3 was 3.46 months.(ABSTRACT TRUNCATED AT 250 WORDS)