Among 122 patients with chronic pancreatitis, marked eosinophilia (greater than 500 eosinophils/mm3 in the peripheral blood) was observed in 21 cases (17.2%). All of the affected patients were males, and there was no significant difference in the incidence of eosinophilia between patients with alcoholic and nonalcoholic pancreatitis. In the patients with eosinophilia, endocrine pancreatic function was maintained comparatively well, despite marked exocrine pancreatic dysfunction. The eosinophilia of chronic pancreatitis frequently developed in association with severe damage to neighboring organs (pleural effusion, pericarditis, and ascites), as well as in association with pancreatic pseudocyst. Our findings suggest that there is a close correlation between marked eosinophilia and severe tissue injury during acute exacerbations of chronic pancreatitis.