Pentosidine, a fluorescent cross-linking compound, accumulates in extracellular matrix, espcially in the collagen, and is formed by the nonenzymatic process of advanced Maillard reaction. We developed a method of determination of pentosidine and tried to examine its level in urine and serum of elder patients. The method, which involves the hydrolysis of samples, pretreatment using a CF-11 cellulose column and HPLC quantification, resulted in a high recovery (94.3%) of pentosidine with low coefficient of variation (8-10%) of total analysis. Serum and urinary levels of pentosidine in control subjects gradually increased with age. Elder patients with cerebral infarction showed higher levels of serum and urinary pentosidine as compared with those with senile dementia and other geriatric disorders. These results suggest that serious damage to systemic vascular tissues has already occurred in these patients due to glycation.