The serum cholesterol and triglyceride levels were measured and the lipoprotein patterns by electrophoresis on cellulose acetate membrane were observed in 30 normal Koreans, 26 patients with cerebrovascular accident, and 18 patients with coronary heart disease. Similar measurements and observations were made in normal Koreas, surgical patients, the patients with cerebrovascular accident and hyperlipidemia in an attempt to examine the effects of body weight, surgical operations, cerebrovascular accident and the administration of clofibrate on serum lipids. The results obtained were as follows. 1. The mean values of serum cholesterol and triglyceride, which shows moderately significant correlation to the body weight in normal Koreans, were markedly higher in the patients with cerebrovascular accident and coronary heart disease than those of control. 2. Serum pre-beta- and beta-lipoprotein patterns in the densitometry of the serum lipoprotein electropherogram of the patients with coronary heart disease were larger than those of control, but the densitometric patterns of the patients with cerebrovascular accident were similar to those of control. Serum pre-beta- and beta-lipoprotein-cholesterol levels of the patients with cerebrovascular accident and coronary heart disease were higher than those of control. 3. Serum hyperlipoproteinemic type IIa and IIb were more frequently observed than type IV in the patients with cerebrovascular accident and coronary heart disease. 4. Serum cholesterol levels decreased to 74.9% of preoperation levels on the 1st postoperative day and recovered to 97.8% of preoperation levels on the 7th day. Serum triglyceride levels started to increase on the 3rd postoperative day, and reached to 115.3% of preoperation levels on the 7th day. After attack of cerebrovascular accident, serum cholesterol and triglyceride levels increased slowly to 121.7% and 133.7% of the each 1st day levels on the 7th day. 5. Serum lipid lowering effect of clofibrate was most conspicuous in the hypertriglyceridemic patients, especially during the 1st and 2nd weeks after initiation of medication, and moderately in the mixed hyperlipidemic patients. Serum pre-beta- and beta-lipoprotein-cholesterol levels were decreased after 8 weeks of clofibrate therapy, but alpha-lipoprotein-cholesterol levels did not change significantly.