BACKGROUND Stenotrophomonas maltophilia is a gram-negative bacillus that has become increasingly recognized as an important nosocomial pathogen, particularly in individuals with severe debilitation or immunosuppression. S. maltophilia is also characterized by its resistance to multiple antibiotics. S maltophilia peritonitis in CAPD (continuous ambulatory peritoneal dialysis) patients is associated with a poor prognosis and loss of CAPD catheter. No report concerning this entity has been presented in Korea. Therefore, we describe and discuss five cases of the S. maltophilia infection associated with CAPD in three patients with peritonitis and two with exit-site infections. METHODS We performed a retrospective search for episodes of S. maltophilia infections related to CAPD in our renal unit. The baseline levels of hemoglobin, albumin, cholesterol, BUN and creatinine were compared with age, sex and, if possible, the underlying disease-matched controls. RESULTS All the patients with S. maltophilia peritonitis had diabetes mellitus as the underlying disease. The individual patients also had other significant combined morbidities, such as panhypopituitarism, COPD chronic obstructive pulmonary disease, cerebrovascular accident and myocardial infarction. The level of hemoglobin in these patients was significantly lower than in the controls, and the mean values of serum albumin, creatinine and BUN were also low. CONCLUSIONS Immune dysfunction due to uremia, anemia, malnutrition, other comorbidities (e.g. diabetes mellitus), and also, an indwelling peritoneal catheter may be predisposing factors for the S. maltophilia infection in CAPD patients. Once the S. maltophilia infection is diagnosed in CAPD patient, the patient should be treated based on the understanding of this particular organism.