SummaryIt was observed that the lung catalase activity of premature (day 21 of gestation; term=22 days) rat pups is affected by maternal iron intake. Pups from control dams receiving Purina Lab Chow and water adlibitumhave only 50% of the lung catalase activity of pups from dams who received 1 mg/kg parenteral iron dextran daily from day 7 to day 20 of gestation. Other oxygen-protective enzymes, copper-zinc and manganese superoxide dismutase, glutathione peroxidase, and glucose-6-phosphate dehydrogenase, were unaffected by maternal iron supplements.