The effect of age and dietary supplementation of vitamin E or N,N'-diphenyl-p-phenylenediamine (DPPD) on organic solvent-soluble lipofuscin pigments (OLP) and glutathione peroxidase (GSH-Px) activity in mouse heart and brain was investigated. Four groups of 32 female weanling mice were fed a basal diet containing either 0, 30 or 300 ppm RR-α-tocopheryl acetate (d-α-tocopheryl acetate) or 30 ppm DPPD from 2 to 18 mo of age. Neither GSH-Px activity nor dietary supplementation of vitamin E or DPPD had an effect on OLP concentrations in the brain or heart. OLP levels were two- to fourfold higher at 12 mo of age in the heart and were lower at 18 mo of age in the brain than at 2 or 9 mo of age. GSH-Px activity increased with age in the heart tissue of vitamin E-deficient and DPPD-supplemented mice only. No change in GSH-Px activity was observed in the brain due to diet or increasing age. These results suggested that OLP concentrations were not affected by dietary supplementation of vitamin E or DPPD but were affected by age-related factors in the mouse brain and heart.