Objective:To investigate the effect of simvastatin treatment on lipid pr of ile and oxidative stress in hypercholesterolaemic Indian population and determine the effect of simvastatin treatment on the activity of paraoxonase(PON).Methods:Analyzed initially before medication administration and four months later after medication.Lipid and lipoprotein measurement were done by enzymatic kits,high density lipoprotein(HDL) was determined by phosphotungstic acid precipitation method and low density lipoprotein(LDL) was calculated by Friedewald’s formula.Lipid peroxidation was measured by three markers namely,conjugated diene,total peroxide,and malondialdehyde.Conjugated diene was assayed by Buege and Aust method.Total peroxide was determined by FOX2 method.Malondialdehyde determination was carried out by Flemming method and total antioxidant status was determined by Ozacan.Paraoxonase activity was determined by measuring the absorbance inrease of p-nitrophenol at 405 nm.Arylesterase activity was calculated from the molar coefficient of 1 310 M~(-1) cm~(-1).Results:Simvastatin significantly reduced total cholesterol,triglycerides,LDL,conjugated diene,total peroxide and MDA levels,where as antioxidant status was significantly increased.Besides,simvastatin significantly increased PON1 activity towards paraoxon.Conclusions:The results from the current study indicate simvastatin may have important antioxidant properties via increasing PON activity. Objective: To investigate the effect of simvastatin treatment on lipid pr of ile and oxidative stress in hypercholesterolaemic Indian population and determine the effect of simvastatin treatment on the activity of paraoxonase (PON). Methods: Analyze initially before medication and four months later after Lipid and lipoprotein measurement were done by enzymatic kits, high density lipoprotein (HDL) was determined by phosphotungstic acid precipitation method and low density lipoprotein (LDL) was calculated by Friedewald’s formula. Lipid peroxidation was measured by three markers namely, conjugated diene, total peroxide, and malondialdehyde. Conjugated diene was assayed by Buege and Aust method. Total peroxide was determined by FOX2 method. Malondialdehyde determination was carried out by Flemming method and total antioxidant status was determined by Ozacan. Paraoxonase activity was determined by measuring the absorbance inrease of p-nitrophenol at 405 nm. Arylesterase activity was calculated from the molar coefficient of 1 310 M ~ (-1) cm ~ (-1) .Results: Simvastatin significantly reduced total cholesterol, triglycerides, LDL, conjugated diene, total peroxide and MDA levels, where as antioxidant status was greatly increased .Besides, simvastatin significantly increased PON1 activity towards paraoxon. Conclusions: The results from the current study indicate simvastatin may have important antioxidant properties via increasing PON activity.