Elevated plasma homocysteine levels may lead to an increased risk for atherosclerosis. Besides genetic factors a deficiency of folate, vitamin B6 and/or vitamin B12 may lead to an increase in the plasma concentration of this sulfur containing amino acid. Homocysteine may enhance by several direct and/or indirect mechanisms the pathogenesis of atherosclerosis. In this review selected aspects of homocysteine in relation to clinical practice will be discussed.