OBJECTIVE To review studies of antibiotic prophylaxis in acute necrotizing pancreatitis published in the last decade and update recommendations. METHODS A search of PubMed (1998-July 2009) was conducted using the terms necrotizing pancreatitis, antibiotics, prophylaxis, and treatment. Clinical studies, meta-analyses, and review articles published in English were included. Additional references were obtained from article bibliographies. Randomized trials published before 1998 were included if indicated. METHODS Relevant studies or meta-analyses on antibiotic prophylaxis since our previous review in 1998 were evaluated; older data were included if still relevant. RESULTS Since our previous review, 4 more randomized trials, including 2 double-blind trials, have been conducted. The blinded studies found no significant difference in mortality with antibiotic prophylaxis compared with placebo, while the unblinded studies found a significant decrease in infections. Given these disparate results, available guidelines and meta-analyses provide different conclusions, usually based on exclusion or inclusion of a single trial. Based on all available data, antibiotic prophylaxis should not be used in patients with necrotizing pancreatitis. Instead, a more measured, on-demand use of antibiotics is preferred. Antibiotics should be added if signs and symptoms of infection are present (eg, fever, leukocytosis, positive results of cultures). Given improvements in intensive care and nutritional support, recent trials have found a lower incidence of infected necrotizing pancreatitis than before. Therefore, future trials are likely to need higher numbers of patients. CONCLUSIONS Use of antibiotic prophylaxis for patients with necrotizing pancreatitis is not indicated, based on 2 blinded trials. Instead, on-demand use of antibiotics appears to be appropriate. Given progress in intensive care and the high crossover rate in studies, the need for antibiotic prophylaxis may continue to be debated for decades.