The aim of the present study was to investigate the effect of donor aging on the glutathione conjugate transport in erythrocytes and whether it plays a role in the resistance to oxidative stress of the erythrocytes of aging subjects. In our comparative study on intact erythrocytes of healthy aging and young adults, in which 2,4-dinitrophenyl-S-glutathione (DNP-SG) was used as model glutathione S-conjugate, we found that the efflux of DNP-SG remained unchanged in the aged subjects. This result suggests that the detoxification function is maintained against the chemical stress employed in erythrocytes of aging subjects. In the assay conditions used, which were optimized to obtain maximal inhibition of glutathione S-conjugate transport, our results also indicated that the susceptibility of erythrocytes to in vitro lipid peroxidation generated by cumene hydroperoxide was enhanced by pretreatment with DNP-SG inhibitors in both age groups. However, the difference in susceptibility was not a function of aging. Further, the results suggested that inhibition of glutathione S-conjugate pump may impair cellular protection of the erythrocytes against oxidative damage.