Fifteen patients (mean age 59.9 +/- 16.1 years) treated by CAPD for a mean of 21.6 +/- 14 months, underwent peritoneal clearances before and after 15 days of intraperitoneal phosphatidylcholine (PC) treatment (50 mg/L). No difference was observed in urea, creatinine, uric acid, and reverse dextrose clearances. A statistically significant increase in phosphate clearances (4 and 6 hr dwell times) (1.36%) and a reduction in drainage volume (2 hr dwell time) (1.36%) were observed after treatment. Urine output and percent dextrose reabsorption were unchanged. The ultrafiltration (UF) showed a tendency to increase, which lasted for 15 days after discontinuation of treatment. This tendency allowed the patients to reduce, during the same period, the amount of hypertonic solution (23.8 L vs. 21.3 L) required. The tendency to increase UF over time deserves further study.