To describe the distribution of homocysteine and prevalence of hyperhomocysteinemia with emphasis on race, sex and age. To determine the extent to which hyperhomocysteinemia is associated with status of folate and vitamin B12. Finally, to describe the relationships between prevalence of hyperhomocysteinemia and prevalence of cardiovascular disease and assess the importance of this risk factor as a cause of vascular disease among US adults. The study was renewed for one year to investigate normal homocysteine concentrations among children and to identify nutritional and non-nutritional determinants of total homocysteine concentrations in children.