The CYBA gene encodes the p22phox peptide, an essential subunit of vascular NADPH oxidases. The aim of the study was to analyze potential interactions between CYBA gene A640G polymorphism and traditional risk factors of atherosclerosis. We studied 320 subjects: 160 patients with coronary artery disease (CAD) and 160 controls. The results of interactions were interpreted on the basis of synergy index values (SI, SIM). The 640G allele interacted with cigarette smoking (SI = 2.02, SIM = 2.32). Even greater increase of the CAD risk was found whenever the 640G allele interacted with both smoking and hypercholesterolemia (SI = 2.70, SIM = 3.60). The results suggest that the A640G polymorphism may influence individual predispositions to CAD through interactions with smoking and hypercholesterolemia.