HLA A, B and C antigens were determined in 128 patients with chronic pancreatitis in Japan. Patients were divided into two groups, chronic alcoholic and chronic idiopathic, from two parts of Japan, the eastern and the western part, with control subjects in each region. A significantly higher frequency of B5 was demonstrated among chronic idiopathic pancreatitis and of B13 among chronic alcoholic pancreatitis in the eastern part, and no definite findings were obtained in the western part of Japan. On the other hand, the frequency of BW 54 was lower among chronic alcoholic pancreatitis in both parts of Japan, but the corrected p value for this antigen was not statistically significant. These facts suggest that 'HLA antigens in chronic pancreatitis have some racial and regional differences.