In order to test the hypothesis that cerebral nuclei showing age-related neuronal depletion would also show signs of vulnerability in their free radical scavenger systems and accumulation of the compounds resulting from peroxidation, the regional levels of a number of compounds were measured in mouse brains. With the exception of the tocopherols all the antioxidants had lower concentrations in the Substantia nigra which showed the most severe neuronal depletion with age. Acetyl-L-carnitine is being investigated as a determinant of neuronal longevity.