Abstract: Objective We investigated the clinical features of secondary peritonitis in patients receiving continuous peritoneal dialysis (CAPD) in order to improve its diagnosis and management. Methods We retrospectively analyzed the clinical data of secondary peritonitis complicated with CAPD in 3 cases, who were admitted to Division of Nephrology, CHCSJ Hospital of Macau between January and April 2003. We also recruited 8 CAPD related peritonitis patients, who were admitted at the same period. We then statistically analyzed their age, duration of CAPD and laboratory data in the two groups. Results In the 3 patients with secondary peritonitis, they were all females with the mean age of 75.3+5.5 years. They had no history of peritonitis before admission, and had been misdiagnosed as CAPD related peritonitis. Abdominal X-ray examination in 2 cases revealed free air in sub-diaphragm area and signs of intestinal obstruction. Surgical treatment was delayed for 3 to 28 days, and finally they were diagnosed as ileum perforation, ischemic necrosis of sigmoid colon, and strangulated incision hernia. Age, hemoglobin, WBC, serum albumin, C-reactive protein, and WBC count in effluent peritoneal dialysate on admission (D1) were similar between the two groups (P>0.05). Patients with secondary peritonitis had the following features as compared with those of CAPD related peritonitis patients: ①longer duration of CAPD (24.6+7.5 months vs 10.5+8.2 months, P =0.035), ② pink effluent peritoneal dialysate found in most cases at the early stage of secondary peritonitis,③ poor response to antibiotic therapy (P <0.05), and ④ higher mortality rate (67% vs 0). Conclusion Patients with secondary peritonitis have clinical features different from those with CPAD related peritonitis. Due to the higher misdiagnosis rate and mortality rate in CAPD patients with secondary peritonitis, differential diagnosis between secondary peritonitis and CAPD related peritonitis should be carefully made in CAPD patients with peritonitis manifestations.