Objective To investigate whether patients, who are at risk of major acute coronary events, are safe to undergo and benefit from early intervention after using simvastatin.Methods The study was a randomized, open, two-dosage-controlled trial to evaluate the safety and benefits of simvastatin administered to 197 patients (10 mg group, n=98 and 20 mg group, n=99), within 48 hours of hospitalization for a diagnosis ofunstable angina or acute myocardial infarction (MI), with total cholesterol (TC)≥180 mg/dL or low-density lipoprotein cholesterol (LDL-C) ≥100 mg/dL. Lipid levels were measured immediately, followed by the 3rd, 6th and 12th month after admission and all adverse events were recorded during follow-up. ), and LDL-C levels fell 13.87% and 19.38% in the 10 mg and 20 rates of achieving target TC reached 26.3% and 36.5% in the 10 mg and 20 mg groups (P<0.01), and that of LDL-C reached 28.2% and 40.3% in the 10 mg and 20 mg groups, respectively (P<0.01). There were higher rates of MI and re-hospitalization resulting from angina pectoris and revascularization in the 10 mg group compared with the 20 mg group.Conclusions The results suggest that early intervention with the HMG-CoA reductase inhibitor, simvastatin, in acute coronary syndromes is possible and safe. It also indicates that the clinical dosage of simvastatin are relatively smaller than that for satisfactory lipid control in patients with acute coronary syndromes.