The aim of the study was to perform peritoneal equilibration test (PET) in predialysis patients, and compared to PET results in patients on chronic peritoneal dialysis (PD). Two groups of patients were enrolled in the study. Group 1: eleven uremic patients who had never been subjected to PD, and group 2: fourteen patients on maintenance PD. The PET was performed as the four hour standard PET, using a 2 liter bag (Dianeal 2.5% glucose) as test fluid. The transport of creatinine through the peritoneum did not differ significantly between the groups corresponding to the dialysate to plasma (D/P) ratios, neither did the glucose ratios differ significantly. After two hours dwell time a significant difference was found in D/P ratio of urea (p = 0.001), in group 1 the median D/P of urea was 0.90 (0.80-1.14) and 0.75 (0.52-0.84) in group 2. No significant difference was found at dwell time zero or four hours. The current study shows that the distribution of PET results is identical in a group of predialysis patients, as compared to a group of chronic PD patients, except for D/P of urea at two hours dwell time.