The role of cyclosporin A in transplantation of composite tissue for potential reconstructive purposes is examined in the rat hind limb transplant model. Two inbred rat strains were utilized. Brown ACI rat hind limbs were transferred to the dorsum of white Lewis rats with microvascular anastomoses. Twenty transplants were divided into four groups for postoperative immunosuppression: control, no cyclosporin; 7 days of cyclosporin; 21 days of cyclosporin; and continuous cyclosporin from 44-113 days. Hemagglutination and antibody titers were measured. Clinical evaluation and histologic examination at sacrifice were performed and rejection graded. Cyclosporin A has been successful in suppressing rejection in composite allograft transplant across defined major histocompatability barriers. Rats treated with cyclosporin A for a short period of time showed signs of rejection after discontinuation of therapy. Five animals treated continuously on cyclosporin A for up to 113 days showed no sign of rejection clinically, histologically, or immunologically.