Increasing evidence suggests that type 2 diabetes mellitus (T2DM) is strongly correlated with Alzheimer's disease (AD). To examine the relationship between T2DM and AD, autoantibodies against amyloid-Abeta were measured in the serum of T2DM patients and age-matched controls. Levels of Abeta autoantibody were measured by ELISA in serum samples of T2DM patients (n=92) and age-matched control group (n=106). Abeta autoantibody levels were increased in T2DM compared with age-matched controls by 45.4 +/- 8.1% (p< 0.001). Females had higher Abeta autoantibody levels than males in both T2DM and control group. Abeta autoantibody levels in the T2DM group were positively correlated with the levels of cholesterol (p=0.011), low density lipoprotein cholesterol (p=0.020), and triglycerides (p=0.039). In conclusion, the level of Abeta autoantibody is dramatically elevated in patient serum of T2DM, and, as such, might be used as a possible biomarker for T2DM.