【Abstract】 Objective To investigate the correlations of changes in leucocytes, T cell subset and albumin in peripheral blood and effluent peritoneal dialysate in continuous ambulatory peritoneal dialysis (CAPD) patients complicated with peritonitis. Methods Twenty-two CAPD patients (12 males and 10 females; mean age of 62.6 years old) admitted to the hospital with CAPD-related peritonitis during the period from Jan. 2006 to March 2008 were enrolled in this study. Leucocytes, T cell subset and albumin in plasma and effluent dialysate were measured after the presence of peritonitis for 1, 3, 6, 9 and 12 days. T cell subset in blood was also examined in 24 healthy individuals (13 males and 11 females; mean age of 62.6 years old). Results In patient’s sera collected at different days after peritonitis, the percentage of CD3+CD8+ was decreased and the ratio of CD4+/CD8+ was increased, as compared with those in normal controls (P<0.05). Positive correlations were found between leucocytes in blood and in dialysate (r=0.404, P<0.001), between CD4+/CD8+ ratio in blood and in dialysate (r=0.976, P<0.001), and between albumin in blood and in dialysate (r=0.434, P<0.001). Bacterial culture in dialysate was positive in 17 patients (77.3%), including Gram-negative bacilli 9 cases (52.9%), Gram-positive cocci 7 cases (41.2%), and fungus 1 case (5.9%). Conclusions In CAPD-related peritonitis, leucocyte increase in dialysate and peritoneal albumin loss were positively correlated, and the increase of blood CD4+/CD8+ ratio indicated the activated cell-mediated immunity. The main pathogens for CAPD-related peritonitis were Gram-negative bacilli.