Plasma and tissue concentrations of pentose-derived glycation end-products ("pentosidine") are elevated in diabetic patients with normal renal function and in both diabetic and nondiabetic patients with end-stage renal disease. To determine the influence of dialysis modality and other clinical variables on the accumulation of pentosidine, we used high-performance liquid chromatography to measure this advanced glycation end-product in plasma, skin, and peritoneal samples obtained from 65 hemodialysis and 45 peritoneal dialysis patients. Plasma pentosidine levels were significantly lower in peritoneal dialysis patients. Concentrations of pentosidine in skin were similar in the two groups. In contrast, peritoneal concentrations of pentosidine were significantly higher in the patients maintained on peritoneal dialysis. Our results demonstrate that dialysis modality influences the plasma and tissue distribution of pentosidine. Compared with hemodialysis, peritoneal dialysis is associated with lower levels of this glycation end-product in plasma, but with higher levels in the peritoneum. The mechanisms accounting for lower circulating levels of pentosidine in peritoneal dialysis patients remain to be determined. Higher levels in peritoneal tissues may reflect chronic exposure to the high concentrations of glucose in peritoneal dialysate.