Renal failure and the need for renal transplantation are more prevalent among patients with diabetes than among other patient groups. Immunosuppressive treatment regimens for post-transplant patients are reviewed, with special emphasis on diabetic patients. The major drugs used are cyclosporine, corticosteroids, azathioprine, antithymocyte or antilymphocyte globulins, and muromonab-CD3 (a monoclonal antibody). Their mechanisms of action, drug interactions, clinical uses in transplantation, and toxicity are reviewed. Some of these drugs will change a diabetic patient's requirements for insulin or oral hypoglycemic agents, and glycemic control during the post-transplant period needs careful monitoring.