Various immunosuppressive regimens were used in an effort to enhance spinal cord regeneration in isologous rats. Ninety-six animals were evaluated six months after transection and immunosuppressive treatment. No evidence of regeneration was found in the control group, in animals inoculated with central nervous system tissue at birth, or in animals receiving some of the immunosuppressive regimens. Injection of 200 mg per kilogram of alpha methyl tyrosine before transection did not enhance regeneration. We did find electrophysiologic evidence of regeneration in one of 13 animals receiving a combination of immunosuppressive drugs and in four of 12 animals receiving one injection of 75 mg per kilogram of cyclophosphamide within one hour after spinal cord transection.