Abstract Alpha 1-antitrypsin infused as fresh whole plasma to 3 emphymatous patients homozygous for hereditary deficiency of this protein was rapidly distributed into the extracellular fluid compartment and then disappeared from the serum with a half-time of 5 to 6 days. The level of alpha 1-antitrypsin was measured by radial im-munodiffusion technique. One patient lacked detectable amounts of this protein in the serum and sputum. After the infusion, small amounts appeared in his sputum. Because of the volume of plasma that would be needed, it is impractical to give whole plasma with the hope of providing potentially protective levels to patients with hereditary alpha 1-antitrypsin deficiency.