Arteriosclerosis and its complications, such as heart attack and stroke, are the major causes of death in developed countries. It was believed that age, hyperlipidemia, hypertension, diabetes and smoking are common risk factors for cardiovascular disease. In 1969, McCully first proposed that homocysteine causes atherosclerosis. His hypothesis was based on the finding of atherosclerosis plaque at autopsies of young people with homocystinuria. There is evidence that elevated homocysteine is associated with higher risk of coronary artery disease. Elevated plasmatic concentration of homocysteine by 5 µmol/l led to increase recurrent cardiovascular event risk by 16 %. Hyperhomocysteinemia is associated with significant risk of stroke, narrowing of the carotid artery due to atherosclerosis and peripheral vascular disease. Hyperhomocysteinemia can by lowered simply by adequate taking of folic acid, vitamins B6 and B12.