Advanced glycation end products (AGE) have been analyzed in aging human peripheral blood lymphocytes since protein glycation and glycoxidation are believed to contribute to the intracellular age-related accumulation of damaged proteins, a process that has been associated with the cellular functional deficits that occur with age. The appearance of AGE in cell lysates was monitored with an enzyme-linked immunosorbent assay using an anti-AGE antibody raised against glycated RNAse. When lymphocyte cytosolic extracts from old donors (86-91 years old) were compared with those from young donors (20-25 years old), a small but significant 40% increase of protein glycation was observed. In both age groups, further analysis of the pattern of glycated proteins by two-dimensional gel electrophoresis followed by western blotting with the same anti-AGE antibody, showed that the protein silver stain and the immunoblot patterns were not superimposable indicating that glycoxidative modifications are targeting only a restricted set of proteins. Among these preferential protein targets, seven of them exhibited a significant age-related increased immunoreactivity with the anti-AGE antibody suggesting that the corresponding modified proteins might serve as biomarkers of aging lymphocytes.