Functional activity of peritoneal macrophages of 50 patients with end-stage renal failure on intermittent peritoneal dialysis (IPD) and of 30 control subjects with normal renal function was determined. Phagocytosis of latex particles by macrophages of dialyzed patients was significantly lower as compared with the controls. Further depression of the phagocytic activity was observed during bacterial peritonitis. Macrophages from the dialyzed patients also showed nonsignificantly decreased functional expression of Fc receptors (FcR) and increased spontaneous nitro blue tetrazolium (NBT) reduction.