The aim of the study was to determine if direct inoculation of peritoneal fluid into Bactec blood culture bottles would improve the positive bacteriological yield compared with conventional techniques in continuous ambulatory peritoneal dialysis (CAPD) patients with peritonitis. All patients presenting with suspected peritonitis had peritoneal fluid injected directly into aerobic and anaerobic Bactec blood culture bottles as well as into sterile culture tubes. Thirty-seven paired samples were analysed. Twenty conventional cultures (54%) were positive compared with 33 (89%) done according to the Bactec system (P < 0.002). In only 1 case did the former technique prove superior. Direct inoculation of peritoneal fluid into Bactec blood culture bottles is therefore superior to conventional methods and has obvious therapeutic implications.