Secretory synovial-type PLA2 (sPLA2-II) in peripheral blood is known to be associated with systemic complications in patients with severe diseases. Being the pacemaking enzyme in eicosanoid synthesis, sPLA2-II is a mediator of the inflammatory response and plays a role in host defense against bacterial infection. We evaluated the clinical role of systemic sPLA2-II in bacterial infection of pancreatic necroses in severe acute pancreatitis. In 58 patients with acute pancreatitis, pancreatic and sPLA,-I and sPLA2-II were measured daily for the first 14 days of hospital treatment by a time-resolved fluoroimmunoassay. All 36 patients with necrotizing pancreatitis underwent regular fine needle aspiration (FNA) to monitor bacterial infection. In 10 patients, infected necroses were found on FNA and postoperative examination. On admission and at most days throughout the observation period, systemic sPLA2-II was significantly higher in patients with infected necroses than in patients with sterile necroses or interstitial pancreatitis. This difference was not found for sPLA,-I, but values were higher in necrotizing pancreatitis than in interstitial pancreatitis at the first 2 days of hospital treatment. If sPLA,-II was >300 ng/ml on 2 successive days within the first 4 days, infected necroses could be predicted with a sensitivity of 89%, a specificity of 8856, and a negative predictive value of 95%. Systemic sPLA2-II has the potential to identify patients at risk of bacterial infection of pancreatic necroses and its routine measurement may therefore, in combination with FNA2 offer a valuable tool in monitoring patients with acute necrotizing pancreatitis.