The purpose of this study was to investigate the effects of the nutrition therapy and drug(simvastatin) treatment on the levels of blood lipids for the hyperlipidemic patients according to genetic polymorphism of apo CIII. Subjects of the study consisted of 43(male: 9, female: 34 )hyperlipidemic patients registered to Kyung Hee Medical Center, Intakes of nutrients for the subjects were determined by 24-hr recall method through a personal interviews. The subjects were instructed to take the hypolipidemic and hypocholesterolemic diets. Compliance was monitored through food records, personal interview, and body-weight measurements. The patients changed their basal diet containing 40. 1g fat(182.7mg cholesterol./day) to a diet containing 30.7g fat(139.2mg cholesterol/day) after 12 weeks of nutrition therapy. The distribution of genotypes for apo CIII by Msp I was 32.5% of TT, 50.0% of TC, and 17.5% of CC. aT the beginning of the study, the level of blood triglyceride was the highest for patients with TT and TC. Following the nutrition therapy, patients with CC exhibited the largest drop of blood triglyceride. Following simvastatin treatment with nutrition therapy, blood LDL-cholesterol decreased in most of the patiens with TT. Meanwhile the distribution of genotypes for apo CII by the Fok I was 10.0% of TT, 47.5% of TC, and 42.5% of CC. The level of blood triglyceride was the highest for patients with CC. Following the nutrition therapy, patients with TC exhibited a significant drop for the blood triglyceride. Following simvastatin treatment with nutrition therapy the level of blood LDL-cholesterol decreased in most of the patients with CC. We concluded that dietary habits and food have been changed by nutrition therapy. And blood lipid levels have been decreased by the restriction of intakes of energy, fat and cholesterol. There was variation in the levels of blood lipids according to apo CII polymorphisms. The level of blood lipids responded to nutrition therapy and drug treatment in different was according to genetic polymorphisms. Accordingly, the choice of individualized therapy based on the patient\`s genetic polymorphism is very important for effective therapy(Korean J Nutrition 33(8) : 813-823, 2000)