Continuous ambulatory peritoneal dialysis (CAPD) is believed to improve the immune competence of end-stage renal failure patients and to increase the risk of graft rejection following subsequent renal transplantation. At this centre, 220 consecutive renal transplants have been studied in patients treated by either CAPD or haemodialysis (HD). Patient and graft survival was not significantly different for the two treatment groups over a five year follow-up. When only first cadaver recipients were considered (152 grafts) one-year graft survival (non-immunological failures excluded) was 77 per cent for CAPD and 79 per cent for HD patients (P greater than 0.05). Time on dialysis and number of pre-operative transfusions were significantly greater for the HD patients (P less than 0.05). A group of HD and CAPD patients were identified as being matched for age, sex, HLA, A, B, DR antigen matches, pre-operative transfusions and time-on dialysis. One-year graft survival of the CAPD patients was 82 per cent and for the HD patients 61 per cent. Studies of patient lymphocyte function and plasma suppressive activity in vitro revealed no differences between CAPD and HD treated patients. CAPD is not an immunological risk factor in renal transplantation and its continued use in the preparation of patients for transplantation is recommended.