Fifty-six patients undergoing orthotopic cardiac transplantation were given Minnesota ALG prophylactically or therapeutically for acute cardiac rejection. During a follow-up period of 0-28 months (mean follow-up period, 11.9 months), the actuarial survival for the entire group was 96% and 86% at 30 days and 1 year, respectively. Actuarial freedom from rejection was 60% and 28% at 30 days and 1 year, respectively. All but seven rejection episodes responded to initial steroid pulses or a modification of a maintenance cyclosporine and azathioprine regimen. The seven failures were rescued with further Minnesota ALG therapy. Few serious hematologic or allergic reactions to Minnesota ALG were observed, and no new malignancies occurred during the follow-up period. We conclude that Minnesota ALG is safe and effective in cardiac transplantation.