Oral phosphatidylcholine at 900 mg/day was given to 4 patients with high lymph absorption for 8 weeks. Fluid and solute transfer before and after treatment were compared to 4 similar controls given placebo. None of the patients had overt ultrafiltration problems. After treatment, overnight peritoneal effluent phospholipid content did not change significantly. Ultrafiltration as well as solute and glucose transfer remained unchanged at the end of 8 weeks. A controlled trial on patients with overt ultrafiltration problems for a longer duration is required to further elucidate the role of phosphatidylcholine supplementation in patients on continuous ambulatory peritoneal dialysis.