In order to investigate the risk factors of ischemic brain stroke (IBS) in diabetic patients, we analyzed 416 cases selected from 6239 diabetic patients admitted to Severance Hospital from Jan. 1983 to Dec 1987. Two hundred and eight cases had IBS. The other 208 cases without IBS were selected as a control group by a stratified random sampling method. The two groups were compared using various clinical characteristics of diabetes mellitus (DM) and known risk factors of IBS. In diabetics with IBS, the duration of DM was longer (9.2 ± 7.1 years), hypertension was more frequently associated (68.2%) and the serum cholesterol level was higher (213.0 ± 55.2 mg/dl) than in diabetics without IBS (7.6 ± 7.1 years, 32.1% and 192.1 ± 44.8 mg/dl, respectively). By means of Stepwise Logistic Regression Analysis (SLRA), it was found that the strong risk factors were hypertension and serum cholesterol level. The serum triglyceride level, type of DM and response to diabetes treatment were also thought to be risk factors of IBS by the retrial of SLRA of residuals after exclusion of hypertension and serum cholesterol level. IBS was not significantly related to the duration of DM, fasting blood glucose level, body weight, glycosylated hemoglobin value, and serum high-density lipoprotein-cholesterol level.