Based on previous work of their own and data in the literature the authors outlined diagnostic and classification criteria of acute pancreatitis. The latter were applied in a prospective study. Thus a group of 71 patients with acute pancreatitis was obtained. In 10 patients of this group at the same time intervals and while the same therapeutic procedures were used, the serum protease levels were followed up. The authors assumed that it will be possible to express thus objectively the severity of the disease and to diagnose in time necrotizing forms of acute pancreatitis. The results re demonstrated the feasibility and suitability of this procedure only for assessment of the severity of the disease.