Objective: Cardiovascular disease (CVD) is the leading cause of death worldwide. The methylenetetrahydrofolate reductase (MTHFR) gene, located on the short (p) arm of chromosome 1 at position 36.3 (1p36.3), might be a possible risk factor for the pharmacogenetics in CVD. A common polymorphism in MTHFR (C677T, Ala -> Val) decreases this enzyme activity and increases the homocysteine concentrations, predisposing one to heart disease. Alternatively, statins, cholesterol-reducing agents, are also used to reduce the homocysteine blood concentrations; the aim of the present study was to evaluate how the genotype frequencies of the MTHFR C677T polymorphism, namely rs1801133, change in the cardiovascular system in patients treated with statin.