Eosinophilic peritonitis is defined as when there are more than 100 eosinophils present per milliliter of peritoneal effluent, of which eosinophils constitute more than 10% of its total WBC count. Most cases occur within the first 4 weeks of peritoneal catheter insertion and they usually have a benign and self-limited course. We report a patient of eosinophilic peritonitis that was successfully resolved without special treatment. An 84-year-old man with end stage renal disease secondary to diabetic nephropathy was admitted for dyspnea and poor oral intake. Allergic history was negative. and physical examination was unremarkable. Complete blood count showed a hemoglobin level of 11.1 g/dL, WBC count was 24,500/mm3 (neutrophil, 93%; lymphocyte, 5%; monocyte, 2%), platelet count was 216,000/mm3, serum BUN was 143 mg/dL, Cr was 5.7 mg/dL and albumin was 3.5 g/dL. Creatinine clearance was 5.4 mL/min. Three weeks after peritoneal catheter insertion, he was started on peritoneal dialysis with a 6-hour exchange of 2L 1.5% peritoneal dialysate. After nine days, he developed turbid peritoneal effluents with fever (38.4 degrees C), abdominal pain and tenderness. Dialysate WBC count was 180/mm3 (neutrophil, 20%; lymphocyte, 4%; eosinophil, 76% [eosinophil count: 136/mm3]). Cultures of peritoneal fluid showed no growth of aerobic or anaerobic bacteria, or of fungus. Continuous ambulatory peritoneal dialysis (CAPD) was commenced, and he was started on intraperitoneal ceftazidime (1.0 g/day) and cefazolin (1.0 g/day). After two weeksr, the dialysate had cleared up and clinical symptoms were improved. Dialysate WBC count decreased to 8/mm3 and eosinophils were not detected in peritoneal fluid. There was no recurrence of eosinophilic peritonitis on follow-up evaluation, but he died of sepsis and pneumonia fifteen weeks after admission.