Characteristics of pathological alterations in long-term peritoneal dialysis (PD) are thickening of submesothelial compact (SMC) zone, small-vessel vasculopathy, and loss of mesothelial cells. Bioincompatible PD fluid plays crucial roles in peritoneal injury. Encapsulating peritoneal sclerosis (EPS), a rare and serious complication, occurred in patients on long-term PD or frequent peritonitis episodes, and ~50 % of EPS developed after PD cessation. We hypothesized that PD-related peritoneal injury factors induced by bioincompatible PD fluid accumulated in the peritoneum and might induce EPS. We therefore examined the accumulation of advanced glycation end products (AGE) and beta 2-microglobulin (β2M) in peritoneum and evaluated the relationship between their accumulation, clinical parameters, and outcome after PD cessation. Forty-five parietal peritoneal specimens were obtained from 28 PD patients, 14 uremic patients, and three patients with normal kidney function. The peritoneal equilibration test was used for peritoneal function. AGE- and β2M-expressing areas were found in vascular walls, perivascular areas, and the deep layer of the SMC in short-term PD patients and extended over the entire SMC in long-term patients. Peritonitis and prolonged PD treatment aggravated peritoneal thickening and the proportion of AGE-expressing areas. The proportion of β2M-expressing areas was increased in long-term PD patients. Thickening of the SMC and the proportions of AGE- and β2M-expressing areas were not related to ascites or EPS after PD withdrawal. It appears that the increased proportion of AGE and β2M deposition induced by long-term exposure of PD fluid may be a marker of peritoneal injury.