Alzheimer's disease (AD) is characterized by the deposition of senile plaques and neurofibrillary tangles in the brain. The presence of the amyloid-beta (Abeta) peptide in senile plaques seems to play a central role in the neuropathology of AD. Diagnosis of AD involves neuropsychological examinations or magnetic resonance imaging and, to date, a specific diagnostic marker indicating AD has not been found. This study analysed anti-Abeta antibodies from the serum of 153 patients with AD using an enzyme-linked immunosorbent assay method. The levels of anti-Abeta antibody from patients in the control group (n=193) were compared with those of patients with AD. Our results showed a significantly lower anti-Abeta antibody level in patients with AD than in the control group. These results showed that the anti-Abeta antibody level in serum could potentially be used to diagnose the presence of AD.