The effect of peritonitis on peritoneal membrane solute transport characteristics was determined as part of a multicenter study in children on continuous ambulatory/cycling peritoneal dialysis. Ninety-three children each underwent a 4-h peritoneal equilibration test (PET) with 1,100 ml/m2 2.5% Dianeal for determination of mass transfer area coefficients (MTAC), dialysate to plasma ratios (D/P) for creatinine and urea at 0, 30, 60, 120, 180, and 240 min and dialysate glucose levels at 0, 30, 60, 120, 180, and 240 min for calculation of D/Do. The mean age of the study cohort was 10.1±5.6 years (range 0.1–19 years). There were 162 historical episodes of peritonitis; at the time of the PET tests, 36 children had never had an episode of peritonitis (group I) while 57 children had a history of one or more episodes of peritonitis (group II). In group II children, the 4-h glucose D/Do was significantly lower and the 4-h D/P creatinine ratio, the creatinine MTAC, and the glucose MTAC were significantly higher (each PPPP=0.07) nearly significantly lower than in children without a history of peritonitis. Linear regression analysis did not demonstrate a correlation between any of the variables and duration of peritoneal dialysis, while the rate of peritonitis was weakly correlated with glucose MTAC (r=0.34, Pr=–0.222, P<0.01). We conclude that children with a history of peritonitis have peritoneal membranes that are more permeable to glucose and creatinine than children without a history of peritonitis, and that the peritoneal membranes of children who have had peritonitis caused by Gram-negative organisms are also more permeable to creatinine and glucose. Such changes are likely to have an adverse effect on membrane function and could eventually contribute to ultrafiltration failure.