Nine hundred and ninety nine patients were admitted in our Department (the Third Department of Internal Medicine, School of Medicine, UOEH) during the five years more since the opening date of the University Hospital (July, 9, 1979), and 864 cases in them (86.2%) suffered from the various digestive diseases. Most of the in-patients with digestive diseases in our Department are resident in Kitakyushu city and its suburbs, especially in Yahatanishi-ku, Wakamatsu-ku and Onga county, therefore, it may be possible to investigate the ecological characteristics of the in-patients of our Department in the relation to the outbreak, clinical course and outcome of the digestive diseases. Namely, it may be assumed that the incidence and prevalence of the idiopathic inflammatory bowel disease (IBD) including ulcerative colitis and Crohn's disease are relatively high in this area (Kitakyushu city and its suburbs) as compared with the average of all Japan. Although the true causes of these illness are still unknown, the inclination of haptoglobin phenotypes (HP) which include 2-2, 2-1 & 1-1 type 1-1 strongly suggests to the association with some genetical factors on the high incidence of these diseases (IBD). In this connection, Hp type 1-1 were recognized 4 in 11 cases (36.4%) with ulcerative colitis, and 3 in 7 cases (42.9%) with Crohn's disease in our Department whereas only 3-5% in normal controls. Secondly, the patients with carcinoma of the biliary tree (bile duct and gall bladder) are relatively more, namely, 17 cases of bile duct cancer and 3 cases of gall bladder cancer were admitted in our Department during this term. It is interesting to note that hepatohilar type of the bile duct cancer was observed comparatively high (4 in 17 cases, 52.9%) in the past five years-more although the etiology is unknown. Finally, several characteristics in liver diseases particularly in viral hepatitis were illustrated in this study, namely, the ratio of transient HBV infection to whole (transient and persistent) HBV infection in the patients with acute viral hepatitis (due to HBV) is high (80.9%), HBeAg positivity is high in chronic B-hepatitis (44.9%), the ratio of alcoholic cirrhosis to whole liver cirrhosis is relatively high (34.9%) and HBsAg positivity is lower in liver cirrhosis due to non-alcoholic origin (mainly due to hepatitis virus) than the average of this country, and also, hepatocellular carcinoma (HCC) without liver cirrhosis is higher (23.0%) than the average of whole Japan (less than 15%) statistically.