SUMMARYThe renal homograft response was studied in 23 goats following four procedures—I. Sham operation, II. thymectomy, III. thoracic duct drainage, and IV. thymectomy and thoracic duct drainage. The technique adopted for thoracic duct drainage allowed diversion of lymph flow to be maintained for 5 days before transplantation, and for the lymphatic flow to be restored to normal thereafter. The homografts in groups II and III failed to show prolongation of survival. Those in group IV showed moderate increases in survival, though the results were not statistically significant. The failure of thoracic duct drainage to prolong survival of renal homografts differs markedly from its effect on skin homografts and there is no evidence that it is of use as a therapeutic measure in clinical renal homotransplantation at the present time. The results following thymectomy and thoracic duct drainage suggest that it may be worthwhile investigating the combination of the former operation with a more potent method of immunosuppression for the control of renal homograft rejection.