Between January 1968 and June 1974 at Newcastle upon Tyne, 63 patients underwent splenectomy in association with transplantation; 45 of these had splenectomy with bilateral nephrectomy before (20) or at the time of (25) transplantation; 18 had post-transplant splenectomy for leucopenia. Mortality was significantly higher in splenectomized patients than in 136 non-splenectomized controls. Of the 63 splenectomized patients, 25 died within 1 year of transplantation, 12 of severe infection associated with leucopenia. Although splenectomy produced a temporary rise in white cell count, leucopenia during the first year of immunosuppressive therapy was not significantly less frequent in splenectomized patients than in controls. There was no significant difference in graft loss between the splenectomy and control groups. It is concluded that splenectomy is contra-indicated in patients who are to undergo renal transplantation and confers no benefit when carried out because of leucopenia developing after renal transplantation.