The question of whether moderately high serum or plasma levels of total homocysteine are a risk factor for coronary heart disease (CHD) and other atherothrombotic disorders has long been debated and is still unclear. The uncertainty mainly stems from the discrepant results obtained in case-control and prospective cohort studies. While case-control study results consistently showed a positive association between hyperhomocysteinemia and atherothrombotic events, prospective cohort studies gave conflicting results.1