The data demonstrate that high plasma homocysteine levels and low plasma folate and vitamin B12 levels are associated with a higher prevalence of coronary artery disease (CAD) in older men and women. Elevated plasma homocysteine levels were observed in 43% of the older men with CAD versus 18% of the older men without CAD, and in 37% of the older women with CAD versus 12% of the older women without CAD.