Administration of 200 mg of D-galactosamine/kg intraperitoneally to rats produced a decrease in the serum concentrations of trypsin and elastase inhibitory capacities. Induction of emphysema by intravenous injection of pancreatic elastase resulted in significantly increased severity of the disease in the animals depleted of alpha 1-antitrypsin. The degree of severity of the disease determined by mean linear intercept suggested a correlation with trypsin and elastase inhibitory capacities at the time of elastase injection.