Fourteen patients with uremia received 17 cadaveric renal allografts following lymphocyte depletion by means of thoracic duct cannulation. As depletion progressed, marked lymphocytopenia appeared, large lymphocytes appeared in the lymph, peripheral lymphoid tissues became depleted in the thymus-dependent areas, immunoglobulin levels remained constant, and delayed hypersensitivity skin responses disappeared. Renal allografting was performed following the removal of as few as 10 x 109 and as many as 331 x 109 lymphocytes. Immunosuppressive drugs were not administered unless allograft rejection occurred or the patient was discharged from the hospital. Little evidence of rejection was noted for as long as 78 days following transplantation. Excellent renal function is maintained in all but one of the nine survivors. The depletion of circulating lymphocytes prior to renal allotransplantation appears to selectively suppress cellular immune defenses and enhance graft survival without seriously depressing humoral defenses.