This study shows that Le rats bearing total bowel allografts treated with CyA (5 mg/kg for 14 days) demonstrated within one month immunological unresponsiveness to donor and third-party alloantigens as determined by MLR responses. Assays performed in long-term survivors (greater than 100 days) showed a continued depressed MLR response to antigen-specific (BN) alloantigens. The response to third-party (ACI) alloantigens was not significantly depressed. After the long-term bowel recipients rejected donor skin grafts, the MLR responses were increased over control, but the transplanted bowel remained intact.