There are a few prospective studies assessing the severity of acute pancreatitis with exclusive criteria for biliary etiology. In a cohort prospective study, Ranson (biliary etiology), Glasgow-modified, APACHE-II, and APACHE-O prognostic criteria were assessed in 65 patients with acute biliary pancreatitis (ABO. Local complications such as necrosis with fluid peripancreatic collection (3 patients), fluid collection with pancreas enlargement (3 patients), pancreatic fistula (1 patients), and pancreatic pseudocyst (1 patients); and organic failure such as renal (5 patients), hemodynamic (3 patients), and respiratory (3 patients) were found. The prognostic criteria performance, according to parameter number or positive variables evidenced that relative risk (RR) varied from 4.7 to 11.2, sensibility from 33.3% to 83.3%, specificity from 79.2% to 98.1%, positive predictive value from 45.0% to 83.3%, negative predictive value from 86.4% to 95.5%, and accuracy from 78.5% to 89.6%. In isolation, most important parameters correlated to severity included white blood cell count >18,000/mm(3), lactate dehydrogenase (LDH) >400 UI/l, 10% drop of the hematocrit, serum calcium <8 mg/dl, increase of urea nitrogen >2 mg/dl, aspartate aminotransferase (AST) >200 mg/dl, LDH >600 UI/l, white blood cell count > 15,000/mm(3), urea > 45 mg/dl, arterial pH <= 7.33 or >= 7.49, creatinin <= 0.6 or >= 1.4, hematocrit <= 30 or >= 45.9, white blood cell count <= 3000/mm(3) or >= 14,900/mm(3). Ranson, Glasgow-modified, APACHE-II, and APACHE-O acute biliary pancreatitis severity criteria all present good sensibility and excellent specificity.