During a four-year period there were 77 episodes and 15 recurrences of peritonitis in 30 children treated with continuous ambulatory peritoneal dialysis for periods of one to 39 months (mean, 15.3 months). The incidence was one episode per 6.0 patient-months. Organisms cultured included Staphylococcus epidermidis (17 episodes), Staphylococcus aureus (15 episodes), and fungi (four episodes). Special culture techniques were needed to ensure a high yield of positive cultures. Peritonitis was usually treated with intraperitoneal administration of cefazolin sodium, and 61% of the episodes were treated at home. There was one death, from Candida peritonitis, and catheters were removed in 11 children because of resistant or recurrent peritonitis (eight cases) or fungal peritonitis (three cases). Peritonitis rates were highest in children who had difficulty performing bag changes aseptically but who could not be transferred to hemodialysis and in hospitalized patients.