The frequency and cause of peritonitis in 18 children receiving continuous ambulatory peritoneal dialysis (CAPD) and nine children receiving continuous cycling peritoneal dialysis (CCPD) are described. Cumulative CAPD and CCPD experience demonstrated 58 episodes of peritonitis in 294 patient treatment months (one case per 5.1 patient treatment months). Total hospitalization for the treatment of peritonitis was 0.18 days per patient treatment month. Life table analysis revealed no significant difference in the peritonitis-free "survival" between the two modalities. Gram-negative organisms accounted for a significantly increased percentage of the peritonitis in CAPD compared with CCPD (65% vs 17%) (P less than 0.001). Thirty-seven percent of the gram-negative infections in the CAPD population were in children with nephrostomies. Factors predisposing to peritonitis were identified in 76% of cases occurring with CAPD. Peritonitis remains the major contributor to the morbidity associated with peritoneal dialysis, regardless of the technique. The resultant frequency of hospitalization is not prohibitive. Attention to the "high-risk" pediatric patient and education directed at several well-recognized predisposing factors may yield improved results.