BACKGROUND: Inoculation of ascitic fluid into blood culture bottles is known to be more efficient than conventional culture method to diagnose spontaneous bacterial peritonitis. The aim of this study is to evaluate recovery and early detection of peritonitis-causing bacteria from ascitic fluid by using the BACTEC blood culture system with bedside inoculation. The results were compared to those of conventional culture method. METHODS: Ascitic fluid specimens from 345 patients suspicious of spontaneous bacterial peritonitis were prospectively evaluated between January 1999 and March 2002. In all cases, 5 to 10 mL of ascitic fluid were inoculated at the bedside into a pair of BACTEC blood culture bottles (BC method), and simultaneously an aliquot of ascitic fluid was sent to microbiology laboratory for conventional culture. Isolated microorganisms and the time elapsed for final report were compared between the two methods. RESULTS: BC method was positive in 66/345 ascitic fluid specimens (19.1%) and conventional culture method in 48/345 (13.9%) (P=0.065). Time elapsed for final report was 82 20.5 hours for blood culture method and 107 42.4 hours for conventional culture method (P=0.002). CONCLUSION: BC method using BACTEC system provides an earlier microbiologic diagnosis of spontaneous bacterial peritonitis than conventional culture method with higher sensitivity.