Atherosclerosis is a chronic inflammatory disease formed by the accumulation of lipids in the innermost layer and large-caliber artery (tunica intima). This accumulation, along with platelet factors, stimulates the proliferation of muscle cells in this region. Over than 400 genes may be related to the pathology since they regulate endothelial function, coagulation, inflammation, metabolism of amino acids, lipids, and carbohydrates. Glutathione S-transferases (GST) are enzymes that catalyze the polymorphic detoxification of metabolites produced by oxidative stress within the cells, which is induced by reactive oxygen species. GSTs are one of the defense mechanisms against oxidative stress damage. Due to genetic, cultural, and environmental factors, the rate of atherosclerosis is higher; however, an early diagnosis is crucial for the prevention and treatment of several complications related to the disease. The present study aimed to analyze the frequency of GSTT1 genotypes regarding the presence or absence of the polymorphism in patients with clinical manifestation of atherosclerosis. We collected 200 samples of peripheral blood of patients with the previous diagnosis of atherosclerosis based on clinical examination and imaging, and 100 samples of peripheral blood to compose the control group of patients without clinical manifestation of atherosclerosis. The polymorphism was assessed by PCR and analyzed on the agarose gel stained with 2.0% ethidium bromide. The frequency of the GSTT1 gene polymorphism was compared using the chi-square test (P < 0.05) and the G-test. In the case group, we detected 85.5% of patients with the GSTT1 genotype present and 14.5% of patients with the null genotype. A significant difference was observed between groups (case vs control) for the presence of the GSTT1 polymorphism. According to the analysis of the variable alcohol consumption, we found that in the case group the presence of the GSTT1 gene was higher in individuals who reported not drinking alcohol. In this study, the presence of the GSTT1 gene polymorphism in male patients with atherosclerosis was 1.5 times higher when compared to female patients. Regarding the variable time of smoking, we found that this genotype was more frequent in smokers for both case and control groups.