BACKGROUND: Previous studies indicated that a recently approved synthetic HMG-CoA reductase inhibitor, atorvastatin, reduces LDL cholesterol and triglyceride. To assess the efficacy on the level of serum LDL cholesterol and other lipoprotein fractions and its safety, we investigated 59 patients for lipid and side effect profile. METHOD: In patients with hypercholesterolemia, who showed 12-hours fasting serum LDL cholesterol>145 mg/dl and <250 mg/dl and triglyceride levels<400 mg/dl were enrolled to diet therapy for 4 weeks. After 4 weeks of diet therapy, serum lipid profile were reevaluated and patients with LDL cholesterol > or =130 mg/dl were assigned to receive 10 mg dose of atorvastatin once daily for 4weeks. After 4 weeks of drug therapy, serum lipid profile were rechecked, if showed LDL cholesterol level> or =130 mg/dl, assigned to receive 20 mg dose of atorvastatin once daily until 8 weeks. RESULTS: Of the 59 patients were assigned to receive atorvastatin therapy, 52 patients completed the study. Among lipid profiles, total cholesterol, triglyceride, LDL-cholesterol and apolipoprotein B levels showed significant reduction with mean reduction rate of 28%, 13%, 38%, 32% respectively after 4 weeks and 31%, 13%, 41% and 34% respectively after 8 weeks. HDL-Cholesterol and lipoprotein (a) level did not show significant change after 8 weeks of therapy. Nine patients had mild adverse events, such as elevated ALT, epigastric pain, insomnia, thumb pain. postural hypotension, palpitation and constipation. Only three patients of fifty-nine withdrew from the study due to adverse events related to drug treatment. CONCLUSION: The atorvastatin was highly effective and generally well tolerated with an acceptable safety profile in patients with primary hypercholestelemia.