Background: The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) have been well established to reduce the risk of cardiovascular diseases. Due to the increasingly high medical expenses in Taiwan, the government has tried several measures to combat this problem. One of the strategies is to promote the utilization of generic drug products. The purpose of this study was to clarify the lipid-lowering effect and cost-effectiveness during conversion of the brand-name simvastatin product (Zocor(superscript ?)) to its generic simvastatin product (Zolotin(superscript ?)) in Taiwanese patients. Method: Electronic data in E-Da Hospital were collected from all patients actively converted from Zocor (20mg/tablet, Merck Sharp ＆ Dohme Pty. Ltd., Australia) to Zolotin(superscript ?) (20mg/tablet, Genelabs Biotechnology Co., Ltd., Taiwan) between January 31, 2005, and July 31, 2006. The dosage of simvastatin remained the same when the Zocor(superscript ?) was converted to Zolotin(superscript ?). The primary effectiveness end point was to compare the preconversion and postconversion low-density lipoprotein cholesterol (LDL-C) levels. The annual price per reduction of 1% of LDL-C with Zocor(superscript ?) and Zolotin(superscript ?) was also compared. Result: A total of 83 patients were enrolled in this study. No significant difference was found in the LDL-C level before and after the conversion. The mean LDL-C- lowering efficacies with Zocor(superscript ?) and Zolotin(superscript ?) were -34.7±15.7% and -36.3 ± 17.7%, respectively (P=NS). However, the HDL-C level after treatment was significantly higher with Zocor(superscript ?) (52.8 ± 12.0 mg/dL vs. 49.8 ± 11.9 mg/dL, P=0.0045). There was no patient in this study with elevated transaminase ＞ 3x upper limit of normal (ULN) value or CK ＞ 10x ULN value under both statin treatments. The average annual cost for reduction of 1% of LDL-C with Zocor(superscript ?) and Zolotin(superscript ?) were 541.0 ± 910.0 New Taiwan dollar (TWD) and 557.0 ± 626.6 TWD, respectively (P=NS). Conclusion: There was no significant difference of the LDL-C lowering efficacy after converting the brand-name simvastatin to the generic product in Taiwan. This study also implicated that it might not be more cost-effective to convert brand-name simvastatin to the generic product in Taiwan if the price of generic drug was not lowered significantly.