Chronic renal failure patients maintained on dialysis have an increased risk for infection. This article summarizes research that has been done on the function of neutrophils (PMNs) and monocytes from chronic hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) patients. The studies involving the HD patients showed that there is a decreased PMN in vitro chemotactic response, decreased C5a receptors on both PMNs and monocytes, and decreased oxidative metabolic responses of PMNs and monocytes to the chemotactic stimuli C5a and formyl-met-leu-phe (fMLP), but not to nonchemotactic factors. The results of studies involving phagocytosis have been conflicting and are discussed in this paper. Due to the basic principles of peritoneal dialysis, this treatment approach depletes the peritoneum of phagocytic cells, adversely affects the function of peritoneal WBCs, dilutes the existing opsonins, and alters the physiologic environment of the peritoneal cavity. Studies of peripheral PMN and monocyte function in CAPD patients have shown that, similar to HD patients, they also have decreased C5a receptors and decreased oxidative metabolic responses to the chemotactic factors C5a and fMLP. Although the factors contributing to the risk of infection in chronic dialysis patients are multifaceted, there are definitely alterations in PMN and monocyte function.