Both (-)-deprenyl and pergolide have been found to induce superoxide dismutase (SOD) in rat striata. There are several reports showing that strains or species with higher levels of SOD live longer. Other studies indicate that (-)-deprenyl can increase life expectancy in rats and that both (-)-deprenyl and pergolide may retard nigrostriatal degeneration. This present paper suggests that all these findings are linked, and that (-)-deprenyl and pergolide possess neuroprotective properties by virtue of an activated removal of toxic oxygen radicals.