Hyperhomocysteinemia, a condition of elevated plasma homocysteine concentrations resulting from impaired sulfur amino acid metabolism, may be a powerful risk factor for occlusive vascular disease. However, little is known about the distribution of hyperhomocysteinemia in the general population. Furthermore, inadequate nutritional status might be a strong determinant of hyperhomocysteinemia, but its importance at a population level (as measured by the prevalence of hyperhomocysteinemia associated with inadequate nutrition) has received little study. Finally, levels of homocysteine associated with elevated risk of vascular disease have not been clearly established.