During a 3-month period, Pseudomonas cepacia was recovered from the peritoneal fluid of 10 patients having chronic dialysis therapy at a peritoneal dialysis center. Six patients developed clinical evidence of peritonitis; one patient developed septicemia. Epidemiologic studies showed that dialysis on specific peritoneal dialysis machines was associated with an increased risk of infection. Laboratory investigation showed contamination of two machines with P. cepacia. Inadequacies in the cleaning and disinfection practices of the automatic peritoneal dialysis machines were identified. Cross-contamination between machines probably occurred through the peritoneal fluid discharge from infected patients during dialysis. Also, the intermittent 2-hour exposure of the machine to 2% formaldehyde may have been inadequate. P. cepacia has not been isolated from the peritoneal fluid of any peritoneal dialysis patient after machine cleaning and disinfection practices were altered.