The pathophysiology of encapsulating peritoneal sclerosis (EPS) that develops after withdrawal from long-standing dependence on CAPD remains unclear. The aim of this study was to clarify the risk factors for EPS as expressed in the peritoneal function. Fourteen patients who had shifted to standard hemodialysis after long-term CAPD (average, 105 months) were studied: 3 developed EPS after PD withdrawal while 11 did not. Analysis of the data obtained from the peritoneal equilibration test (PET) revealed that: (1) the dialysate/plasma creatinine ratio (D/Pcr) was significantly higher in the EPS group than in the non-EPS group during the course of PD as well as after PD withdrawal; and (2) eight patients, including the 3 with EPS, were classified as being in a high-transport membrane state (HTS) at PD withdrawal. The duration of HTS during PD was longer in those patients with EPS. During the periods after PD withdrawal, none of these EPS patients recovered from HTS, whereas 4 of the 5 non-EPS patients did. These data suggest that long-standing HTS during the course of PD as well as post-withdrawal, may be risk factors for EPS development. For this reason, it is indicated that PET has clinical relevance in examining sequential changes in peritoneal function and in detecting those patients at risk of EPS.