We have assessed the clinical significance of exit-site infections secondary to Xanthomonas maltophilia in continuous ambulatory peritoneal dialysis (CAPD) patients, and compared them with episodes due to Pseudomonas. The study was a retrospective survey of all episodes of Xanthomonas and Pseudomonas-related exit-site infections (ESI) in all patients treated in our unit between 1984 and 1992. Thirteen episodes of Xanthomonas-related ESI were observed in eight patients and 17 episodes of Pseudomonas-related ESI were seen in 15 patients. Xanthomonas-related ESI was frequently associated with other microorganisms, while Pseudomonas-related ESI was not (66% versus 5%, P < 0.02). Only one episode of Xanthomonas-related ESI resulted in peritonitis and subsequent catheter removal, after 15 months of resistant colonization. Another case was considered to be chronic and indolent, as the Xanthomonas-related ESI continued after 23 months of local treatment. The other 11 episodes were resolved either without treatment or with an antibiotic cream after 7-120 days. However, all but two episodes of Pseudomonas-related ESI required intravenous antibiotics (usually ceftazidime); seven patients developed peritonitis, and 11 required surgical catheter manipulation (five external cuff extrusion, and six catheter removal) (1/13 Xanthomonas-related versus 11/17 Pseudomonas-related ESI, P < 0.03). Most Xanthomonas-related ESI do not lead to peritonitis, and constitute a mild condition, easily treatable without parenteral antibiotics or catheter replacement. The appearance of other associated organisms and the favourable evolution with local treatment suggest a saprophytic behaviour for Xanthomonas in our CAPD patients. On the contrary, Pseudomonas-related ESI is usually severe, requires parenteral antibiotics, frequently leads to peritonitis, and requires catheter replacement.