Data on the serum level of advanced glycation end products (AGEs) in Alzheimer's disease (AD) patients are scarce, although a specific biochemical marker easy to detect in body fluids is desired for an early diagnosis of disease and to monitor the effects of therapeutic treatment. In the current study, the content of AGEs was examined with an immunochemical assay in the sera of AD patients, in the frame of a search for a biochemical marker of disease. Subjects with AD and vascular dementia (VaD) were included in the study (n = 30; age range, 68-70 years). The results were compared to the healthy control groups. The enzyme-linked immunosorbent assay (ELISA) inhibition test for the determination of AGEs is based on a rabbit anti-AGE, affinity-purified antibody and a model AGE-myoglobin antigen, in which a serum sample treated with proteinase K is used as an inhibitor. For the measurement of immune complexes and anti-AGE antibodies, the corresponding ELISA tests have been applied. The AGE level in the VaD group (49.5 U(AGE)) was higher than in AD patients (46.1 U(AGE)). The level of total AGEs in the sera of AD patients was significantly lower than in the control group (50/51.6 U(AGE)). These relations were not observed with regard to the immune complexes and anti-AGE antibody levels in AD (70.2 U(IC)/0.027 U(IgG)) and VaD (83 U(IC)/0.034 U(IgG)) patients because the levels of these parameters were similar to the controls (76.2 U(IC)/0.042 U(IgG)). The work revealed the lower level of circulating serum AGEs in patients with AD in relation to healthy controls.