Influence of age on lead-induced oxidative stress was investigated in young, adult, and old rats maintained on 0.2% lead acetate (2000 ppm lead) in drinking water for 3 mo. The lead-induced depletion of blood and liver reduced glutathione was about equal in young and adult but not in old rats. The increases in blood, liver, and brain oxidized glutathione and blood and liver superoxide dismutase levels were related to the accumulation of lead in these tissues and followed the order young > adult > old. The lead-induced inhibition of blood delta-aminolevulinic acid dehydratase activity, lowering in hemoglobin, and enhanced urinary excretion of delta-aminolevulinic acid were independent of variation in age. The results indicate that young rats may be most sensitive, whereas old rats may be most resistant to some of the oxidative effects of lead examined, which may be related to the accumulation of lead.