Although the incidence of insulin-dependent diabetes mellitus (IDDM) is greatest in the early teenage years, the disease may have its onset much later in life. Approximately 25 to 30% of patients develop the disease after the age of 20 years. Most patients with NIDDM are obese, but type ipatients vary from normal weight to wasted depending on the length of time between onset of symptoms and start of treatment. A total of 213 Korean IDDM patients, aged over 20 years, who visited and/or admitted to the following hospitals and medical centers from January to December of 1992 were recruited: Seoul Eulji Hospital, Kyunghee Medical Center, Seoul National University Hospital, Yonsei University Severance Hospital, Chungsang University Pildong Hospital, Chungnam National University Hospital, Kyungbuk National University Hospital, Pusan National University and Chonnam National University Hospital. The percent ideal body weight(%IBW) and body mass index(BMI) at the time of the study were obtained. Also, the percent maximal ideal body weight(%IBWM) and maximal body mass index(BMIM) were derived from the past maximal body weight by taking down the subject's weight histories. Other clinical characteristics such as age and sex distributions were analyzed. And laboratory findings including serum lipids and HgbA1c were determined. The results were as follows: The levels of serum total-cholesterol and LDL-cholesterol ere significantly higher in the female subjects than those in the male subjects. 32.9% of the subjects had a serum LDL-cholesterol level above 160 mg/dl, and 23.0% had a triglyceride level above 200 mg/dl. Positive correlations were observed between obesity and lipid level except HDL-cholesterol. 39.9% of the subjects had a %IBW or % IBWM over 120% more than once. 39.4% of the subjects were above gradei obesity in BMI or BMIM at least once. The prevalence of obesity was significantly higher on female than in male subjects: Male subjects who had a BMI higher than 27 were 8.1% and female subjects who had a BMI higher than 25 were 38.6%.The prevalence of obesity and hyperlipidemia in Korean adult insulin-dependent diabetic patients was much higher than excepted. And above results support the notion that maintaining adequate ideal body weight through proper diet control, insulin therapy and education should be emphasized.