Hyperhomocysteinemia has recently emerged as a potentially major risk factor in the pathogenesis of coronary artery disease. Various genetic and nongenetic factors influence plasma homocysteine status. The mechanism associating hyperhomocysteinemia with atherosclerosis, if any, is still unclear, but homocysteine may have an adverse effect on vascular endothelium. Folic acid in low doses may ameliorate this process. Several studies are examining the influence of homocysteine-lowering therapy with folic acid on the risk of atherosclerotic vascular disease.