Background: There are very few prospective studies on the hyperlipidemia among Korean patients in primary care. In order to investigate the safety and efficacy of simvastatin after 24-week treatment among Korean patients with hyperlipidemia in primary care setting, a multicenter prospective study was carried out. Methods: A total of 1,067 patients were enrolled from 46 family physicians for the period of one year from January 1999 to January 2000. Following 4 weeks washout, eligible patients were treated with Simvastatin administered orally for 24 weeks. To ascertain the compliance and safety, we regularly followed the patients up at the interval of 4, 12, 24 weeks after screening. Total cholesterol (TC), HDL-cholesterol and triglycerides assays were performed at 0, 12 week. For the adverse events evaluations, physicians examined patients after patients filled up the questionnaire when they visited. Also diet therapy was maintained continuously during the study. Results: Among 1,067 hyperlipidemic patients, 1,019 patients (male:368, female:651) were evaluated for safety assessment and 597 for efficacy assessment. During the first 24 weeks of treatment, the lipid-lowering medication was continued by 52.3% and discontinued by 19.7%. The remaining 28% were dropout. After the first 12 weeks of Simvastatin medication, total cholesterol, triglycerides and LDL-cholesterol levels showed significant reduction of 23.2±12.5%, 4.8±51.7%, 33.0±18.8% respectively (P<0.05) and HDL-cholesterol rose significantly to 9.6±98.5% (P<0.05). Total 93 adverse events (9.1%) were reported in 1,019 patients. Most frequently reported adverse event was indigestion (1.1%) and followed by heartburn (1.0%), myalgia (0.7%),
puffiness (0.7%) and weakness (0.6%). Conclusion: Compliance with the lipid lowering therapy was relatively low in primary care and simvastatin effectively controlled hyperlipidemia and was well tolerated.