A prospective study was performed to evaluate two culture methods for the diagnosis of bacterial peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD): a total bag volume method, and culture of 50 ml with prior saline wash. Peritonitis was present in 45 patients (47.4%). The wash method was more sensitive (80%) than bag culture method (62.2%), specially in patients with antimicrobial drugs therapy (p < 0.05). Therefore, specificity was greater for the bag procedure (78% vs. 62%).