Diabetes mellitus is a heterogenous carbohydrate metabolic disorder, of which clinical characteristics are different depending on race, age, economic condition, and other environmental factors. The Korean diabeteics also have characteristic features which differ to another country. We studied inpatient diabetics who admittied from 1984 to 1988 in St. Benedict hospital. We examined fasting plasma glucose (FBS), 2 hour postprandial plasma glucose (PP2), total cholesterol, triglyceride. We classified the patients into four groups (obesity group, overweight group, normal weight group, under- weight group) according to the weight on the admission day and compared above parameters with this group. We also analysed the admission causes of the patient including frequently admitted patients. The results are follow; 1) The total infatients number during five years is 9, 315 among which 444 patients were diabetics (4.8%). 2) The male to female ratio is 1:1.07. In obesity and overweight groups, the ratio is 1:2,1, 1:1,31 respectively. In normal and underweight groups, the ratio is 1:0. 87, 1; 0, 1 respectively. 3) The peak incidence occurred in 6th decade (34.9%). And the next are 7th decade (22,6%), 5th decade (19. 5%) in order. 4)The number of obesity group is 120 patients (23.0%). 5)The average FBS on admission day of underweight group is significantly increased than those of normaI, overweight and obesiity groups. (p<0.05) 5) The average PP2 on admission day of underweight group is significantly increased than those of normal, owerweight and obesity groups. (p<0.05) 7) The ratio of hypercholesterolemia is 23% in male patient and 49.1% in female patient, the ratio of hypertriglyceridemia is 27% in male patient and 35% in female patient. 8) The most common cause of admission is to contral hyperglycemia, the next are to control infections (including pulmonary tuberculosis), neurophthy, nephropathy, cardiovascular system complications. 9) In obesity and overweight groups, to control car diovascular system complication is relatively more common cause, but in normal and underweight groups, to control neuropathy is relatively common cause. 10) The most common cause of admission of frequently admitted patients is to control pulmonary and urinary tract infections. The next are are to control hyperglycemia, cardiovascular system complicatians, neuropathy and diabetic coma.