We investigated influences on glycemic control in 177 diabetic patients after The Great Hanshin-Awaji Earthquake which occurred on January 17, 1995. Changes in serum HbA(1c) level were studied according to the worsen rate of dietary and living conditions. A significant temporary increase in the mean value of HbA(1c) level was found after the earthquake (8.34 +/- 2.07% in March, 1995 vs. 7.74 +/- 1.82% in December, 1994, P < 0.01). Ninety nine of them showed more than 0.5% in the rate of increase. Multiple regression analysis was applied to the following factors: inappropriate diet, discontinuation of drug uptake, reduction of exercise, destruction of house, long stay at shelter, sex, age, and pre-earthquake therapy. Among them, inappropriate diet demonstrated the highest partial regression coefficient to raise the mean value of the HbA(1c) level. The increased level of HbA(1c) declined gradually to the pre-earthquake level in September, 1995. This study emphasizes the importance of appropriate diet for diabetic patients during a natural disaster. To fulfil it, medical staff have to educate diabetic patients of their disorders tediously in ordinary time. In addition, it seems quite useful to supply a medical information card and a small medical bag containing essential drugs to each patient.