Continuous recirculating peritoneal dialysis (CRPD) was newly introduced to improve solute removal efficiency in conventional dialysis therapies such as hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD). In CRPD, a part of the dialysate in the peritoneal cavity was drained through a double-lumen catheter and purified by an extracorporeal dialyzer. Urea removal characteristics in CRPD were examined in a canine study. In this study, a recirculation-dialysis experiment using a dog weighing 9.0 kg was carried out under 100 and 200 ml/min of flow for recirculating and delivered dialysates, respectively. An FB-50H (Nipro Medical Industries, Ltd., Osaka, Japan) composed of cellulose diacetate membrane with 0.5 m2 of surface area and Dianeal-1.5 (Baxter Limited Laboratories, Tokyo, Japan) containing urea were used as the extracorporeal dialyzer and dialysate. Urea peritoneal and dialyzer dialysances (DBP and DBD) were 3.05 and 33.3 ml/min by computer simulation using a compartment model for CRPD. This DBP value can be estimated as 20.3 ml/min for a 60 kg human. From this result, time-averaged value for BUN over an 8 hr/day CRPD, combined with three exchanges/day as CAPD is estimated to be 34.3 mg/dl, which is much lower than 45.2 mg/dl for a 12 hr/week HD, or 53.0 mg/dl for conventional CAPD.