In the peritoneal dialysis, it is well-known that the peritoneal permeability increases gradually over the duration of treatment. The enhancement of the peritoneal permeability causes an under-dialysis and ultrafiltration failure, which is one of the grave factors which disrupt the homeostasis of body fluid. Hence, the monitoring of the peritoneal permeability is very important in order to give each patient some better prescriptions. In this study, we designed a novel criterion which can evaluate quantitatively the peritoneal permeability by applying a kinetic model for the peritoneal dialysis. Moreover clinical implementations of the novel criterion were validated with using the clinical data. By employing PD NAVI (JMS Co.,Ltd., Hiroshima, Japan), 50 well-being peritoneal dialysis patients performed the peritoneal function test including the peritoneal equilibration test (PET), which measured both urea and creatinine concentrations in the dialysate and drainage volumes. The overall mass transfer area coefficient for urea (MTACu) and that for creatinine (MTACc) were determined from a peritoneal mass transfer model and the clinical data for each patient. An average of MTACu/c which is the ratio of MTACu to MTACc was 1.78 and a standard deviation of that was 0.32. MTACu/c correlated with the drainage volume of PET (r2>0.66). Moreover a decrease of MTACu/c showed the enhancement of the peritoneal permeability (p<0.0001). Furthermore, since MTACu/c implies a peritoneal diffusive selectivity, MTACu/c also correlated with dialysis outcomes such as Kt/V for urea and weekly creatinine clearance normalized to 1.73m2. Then, we could derive some recommendations for MTACu/c by applying the recommendations for the dialysis outcomes such as NKF-DOQI guideline. Thus, MTACu/c can evaluate not only the peritoneal permeability, but also the dialysis outcome. We proposed that MTACu/c is available as the criterion which manages the peritoneal permeability and the therapeutic efficiency of the peritoneal dialysis.