Most attacks of acute pancreatitis are self-limiting, but in 10-20% of cases, however, severe diseases with systemic complications develop. During the last few years, it has been recognized that acute phase proteins have an important role in the pathophysiology of acute pancreatitis. The present study examines the value of C-reactive protein, alpha-1-antitrypsin and orosomucoid in the assessment of severity of acute pancreatitis.150 adult patients suffering from acute pancreatitis by Mayer's clinical criteria (10) were divided in two groups. The first one (n = 50) consisted of patients with severe form of the disease and the second (n = 100) of patients with a mild form of acute pancreatitis. Acute phase proteins (C-reactive protein, alpha-lantitrypsin and orosomucoid) were determined quantitatively in both groups on the 1, 2, 3, 7 and 14th day of the disease onset.Increase in C-reactive protein values was observed in both groups. There was statistically significant greater increase in C-reactive protein in patients with severe acute pancreatitis than in those with mild form of the disease. C-reactive protein values fell slowly in all patients. Serum alpha-1 antitrypsin values were less increased than C-reactive protein values. There was a greater increase in patients with severe form of disease. The increase of orosomucoid was seen only after the third day of the disease onset and there was not a significant difference in values between the two groups.One of the most important problems in treating patients with acute pancreatitis is to detect patients with a severe form of the disease as early as possible, so that adequate treatment can be started immediately. The severity of acute pancreatitis is graded by Ranson and Imrie scores, but they request 48 hours for prognosis to be defined. Despite intensive research, no single laboratory test or pathophysiologic parameters have been found to accomplish early diagnosis. Recent studies suggest that single biologic markers such as acute phase proteins may soon allow a simple and early assessment of the prognosis.This study suggests that a C-reactive protein is a good early marker for the severity of acute pancreatitis. The high increased levels at the beginning point to serious course of disease in future. The increase of alpha-1-antitrypsin is of a similar importance, while the increased orosomucoid, appearing only after the third day, is of no importance in relation to the prognosis of the disease.