D-Penicillamine administered orally in daily doses of 300 mg or 400 mg to pregnant rats during the last six days of gestation caused marked growth retardation, a decrease in the lung weight to body weight ratio and histological features characteristic of pulmonary emphysema in the newborn animals studied. It was also demonstrated that a normal diet given to the dams for a period of three weeks after delivery did not restore the lung tissue of the offspring to normal.