Background: Statins have multiple actions, independent of their classical effects on lipoprotein. However, the data about the effects of statins on insulin sensitivity remains controversial. The aim of this study is to evaluate the changes in insulin resistance in dyslipidemic patients treated with various statins. We also observed the difference between the groups with and without improved HbA1C after statin therapy. Methods: The study group comprised 1432 consecutive subjects who were newly treated with statins visiting cardiovascular center of KUMC Guro-Hospital. We measured lipid profiles(HDL, LDL, total cholesterol) and fasting plasma glucose and insulin levels before, after 1 year and after 2 years of statin treatment. Insulin resistance was assessed by calculating Homeostasis assessment model (HOMA) Results: A total of 20.9% were treated with Rosuvastatin, 29.7% with atrovastatin, 8.8% with Pitavastatin, 20.3% with Simvastatin, 4.7% with Fluvastatin, and 7.6% with paravastatin. Fasting plasma triglycerides total and LDL cholesterol were significantly reduced when compared with baseline. But HOMA-IR increased (from 46.36 to 60.68, 33%, P=0.000) regardless of types of statin and the fasting plasma level of glucose, insulin and HDL cholesterol did not change after statin therapy. When compared with baseline, Fluvastatin and Pitavastatin significantly increased HbA1C but, Atrovastatin, Rosuvastatin, simvastatin and Paravastatin did not. There were no different variables between the groups with and without improved HbA1C Conclusions: The present study demonstrates that despite of improvement of lipid profiles(LDL, Total cholesterol) insulin resistance could be worsened by statin treatment in dyslipidemic patients. Nevertheless, further studies are needed to clarify the effects of statins on insulin sensitivity.