Background: Peritonitis is an important complication in continuous ambulatory peritoneal dialysis (CAPD) patients. Procalcitonin (PCT) has recently been identified as an inflammation marker and recommended as a new potential marker in CAPD peritonitis. We aimed to study a card test for PCT and compare the results with the conventional markers such as C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and white blood cell (WBC) count. Patients and methods: A total of 40 CAPD patients; 20 patients with an episode of peritonitis and 20 patients without any clinical or laboratory sign of infection were included in the study. PCT, CRP, ESR, WBC and dialysate cell count were performed at the beginning of the clinical signs of peritonitis. Results: CRP and ESR had the highest sensitivities (100% for both) but lower specificities (55 and 10%; respectively) and PCT had the highest specificity with a relatively low sensitivity (100 and 70%) according to the calculated results. Conclusions: The card test for PCT seems to be suitable for the adjunctional use in CAPD peritonitis, with its shorter turn-around time, appropriateness for nearpatient testing and high specificity. © 2007 The Association for Clinical Biochemistry.