Early recognition of severity of acute pancreatitis is very uncertain. For this reason it is necessary to have objective criteria to predict with accuracy the course of the disease. The aim of this study was to examine the value of the determination of the acute phase reactants: C reactive protein (CRP), alpha 1-antitrypsin (alpha-AT) and alpha 1-glycoprotein acid (alpha-GA) as prognostic indicators of acute pancreatitis on admission and on the third day. We have studied 40 patients with acute pancreatitis and serum concentrations of CRP, alpha-AT and alpha-GP were related to the Ranson Index. On admission the median levels of CRP: 74 mg/L, alpha-AT: 208 mg% and alpha-GA: 303 mg% were significantly higher (p less than 0.001) in patients with Ranson Index greater than or equal to 3 than in those with Ranson Index less than or equal to 2 (CRP: 166 mg/L, alpha-AT: 303 mg% and alpha-GA: 121 mg%). The values which differentiated patients with better and worse prognosis were: CRP 100 mg/L (sensitivity 100% and specificity 86%); alpha--AT 275 mg% (sensitivity 71% and specificity 85%); and alpha-GA 90 mg% (sensitivity 87.5% and specificity 57.9%). CRP, and to a lesser degree the alpha-AT and alpha-GA, were related to the duration of the ileus, and to the severe complications of the acute pancreatitis.