Three cases of "sterile" peritonitis in CAPD patients are discussed, where the predominant white cell type in the peritoneal dialysis fluid was the eosinophil. No bacterial or fungal organism was isolated on repeated culture of the dialysis fluid and all had a benign course. The eosinophilic response appears to occur very soon after starting CAPD, is relatively asymptomatic and does not require antibiotic therapy. It is suggested that the eosinophilia is related to allergy to some constituent of the peritoneal dialysis system.