Cognitive impairment in elderly diabetic patients has generated considerable interest recently; however, the mechanism of the impairment remains to be elucidated. In the current study, factors associated with cognitive dysfunction in old diabetic patients were explored. A Mini Mental State Examination (MMSE) was performed on 907 of 1173 registered elderly Japanese diabetic subjects. To characterize the clinical features of diabetes, we examined indices of glycemic control, lipid metabolism, blood pressure and complications. Single regression analysis adjusted for age showed that shorter height, higher GDS 15 scores, lower serum albumin, history of cerebrovascular disease, the existence of diabetic nephropathy, no smoking habit, no drinking habit, and no occupation were associated with lower MMSE scores. Multiple regression analysis demonstrated that age (odds ratio (OR)=1.079; 95% confidence interval (CI)=1.011-1.150), GDS 15 scores (OR=1.139; 95% CI=1.045-1.243), serum albumin (OR=0.336; 95% CI=0.174-0.745), and history of cerebrovascular disease (OR=3.011; 95% CI=1.578-5.748) were the variables significantly associated with having lower MMSE scores.