Infection of pancreatic necrosis is the most dangerous complication of acute necrotizing pancreatitis. Infection is undoubtedly caused by the endogenous flora of the host. This is why prophylaxis with a broad-spectrum antibiotic is considered an effective procedure. However, two aspects should be taken into consideration when choosing the antibiotic; it should have the spectrum of action consistent with the pathogens and it should penetrate effectively to the necrotic tissue of the pancreas. The aim of the study was to estimate the efficacy of piperacillin/tazobactam penetration into pancreatic necrosis in patients who received intravenous infusion of piperacillin/tazobactam at a dose of 4.5 g every 8 h for 14-21 days, as the prophylaxis in the treatment of acute necrotizing pancreatitis.Necrotic tissue of the pancreas and the inflammatory ascites surrounding the pancreas were derived from 15 patients (male, 10; female, 5; mean age 46 years), who underwent laparatomy due to pancreatic necrosis after treatment for 14-21 days. Tissue/fluid samples were investigated for the concentration of the antibiotic by fluoroscopic/spectroscopic methods of registration in an HPLC system.The mean concentration of piperacillin/tazobactam was established as 120 mg/kg (SD+/-34) in the necrotic pancreatic tissue and as 183 mg/kg (SD+/-37) in the inflammatory pancreatic ascites.In patients with acute necrotizing pancreatitis, the study indicates effective penetration of piperacillin/tazobactam to the necrotic pancreatic tissue and to the inflammatory ascites surrounding the pancreas.