AbstractType 2 diabetes mellitus and higher total plasma homocysteine concentrations are each associated with an increased incidence of cardiovascular disease and with diminished cognitive performance. Relations between homocysteine concentrations and cardiovascular disease incidence are stronger in the presence of type 2 diabetes mellitus. Therefore, we hypothesized that relations between homocysteine concentrations and cognitive performance would be stronger in the presence of type 2 diabetes. We related homocysteine concentrations and cognitive performance on the Mini-Mental State Examination in 817 dementia- and stroke-free participants of the Maine-Syracuse Study, 90 of whom were classified with type 2 diabetes mellitus. Regardless of statistical adjustment for age, sex, gender, vitamin co-factors (folate, vitamin B