The aim of the study was assessment of theoretical possibilities of the Automated Peritoneal Dialysis (APD) optimization. The analysis of influence of dwells number modification and peritoneal transport character on Nightly Intermittent Peritoneal Dialysis (NIPD) efficacy and adequacy was performed. 20 patients were included in the study. The velocity of urea peritoneal transport expressed as SMTR (solute mass transport rate) was calculated according to the formula: SMTR = delta (CDVD)/delta t, where: delta (CDVD)--change of urea mass in dialysate during delta t time (CD-urea concentration in dialysate, VD-intraperitoneal volume of dialysate). VD was estimated from dilution of volume marker (RISA). On the basis of SMTR, the dialysis efficacy expressed as total dialysed urea and dialysis adequacy expressed as Kt/V were estimated. The values of listed parameters were calculated for the different NIPD schedules (4-9 dwells during 8-hours session). It was revealed that the shortening of dwell time with simultaneous multiplying of dwell numbers resulted in increase of dialysis efficacy and adequacy. However, this improvement was non-proportional to the increase of dialysis solution volume and it did not provide the optimum of dialysis nor recommended level of adequacy even during the session consisting of 9 dwells. There were no significant differences of Kt/V values between subgroups of patients with different character of peritoneal transport assessed according to PET test. The tendency to achieve the recommended values of Kt/V was observed in high transporters group. The results of the study indicate the large capabilities of APD optimization. The direct measurement of peritoneal transport velocity allows to provide better individualization of PD program. The prediction of APD efficacy and adequacy on the base of presented method seams to be an interesting alternative.