Introduction: Some factors such as peritonitis can cause decrease ultrafiltration and adequacy of peritoneal dialysis. Serum (PTH) and calciumphosphor (Ca-P) product can result in extraosseous calcification such as calcification of peritoneal membrane. The aim of this study is to evaluate of effect of serum (PTH) and Ca-P product on membrane function in CAPD patients.Methods: A multicenter, retrospective cohort study was carried out on 1284 patients receiving CAPD at least three months. According to first six months measurement of serum (PTH) and Ca-P product, patients were calcified into three groups ((PTH)<150, (PTH) between 150 to 300, and (PTH) ³ 300) and two groups (Ca-P product<55, Ca-P product ³ 55), respectively. According to classified (PTH) and Ca-P product, the baseline GFR, total Cr clearance, Kt/v and UF were compared with the last these variables.Results: The mean age was 51 ± 16 (18 to 92 years).Patients had (PTH)<150, 52%, (PTH) between 150 to 300, 33%, and (PTH) ³ 300, 14%. Ca-P product<55 and ³ 55 were in 67% and 12% of patients, respectively. In the end of the study, patients with Ca-P product ³ 55 had more frequency of total Cr clearance<70 and Kt/v<2.1 compared with patients with Ca-P product<55 (57% versus 37%, P<.0001) and (65% versus 45%, P<.001).There was no difference between Ca-P product groups regarding GFR. There were no differences between (PTH) groups regarding last Kt/v, total Cr clearance, and GFR.Conclusions: High serum Ca-P product can decrease Kt/v and total Cr clearance. However, serum (PTH) has no effects on PD adequacy and GFR.