Immunological approaches have been used to demonstrate the presence of advanced glycation end-products (AGEs) in several human and experimental animal tissues. We previously prepared polyclonal and monoclonal anti-AGE antibodies by immunizing AGE-modified proteins such as BSA and RNase. Although these antibodies contributed to demonstrate the presence of AGE-modified protein in vivo, the epitope structure of these antibodies had not been identified. We subsequently prepared several antibodies against AGE structures such as pentosidine, pyrraline, 3-deoxyglucosone imidazolone and N epsilon-(carboxyethyl)lysine by immunizing single AGE structures. These structure-specific antibodies have greatly helped broaden our understanding of AGE structures in aging and age-enhanced disease process. Monoclonal anti-AGE antibody is also used for the identification of major AGE structures in some pathological tissues, such as human atherosclerosis lesions. Based on the strategy, we successfully identified a novel AGE structure named glycolaldehyde-pyridine, which is the major antigenic AGE derived from glycolaldehyde. Therefore a monoclonal antibody library for AGE structures has served an important role in the elucidation of the biological significance of AGE.