Alpha 1-proteinase inhibitor (also known as alpha 1-antitrypsin) derived from pooled human serum (Prolastin, Miles Biologicals) has been available in the United States since 1988. Although no formal controlled prospective study has been performed to prove its efficacy, intravenous administration of Prolastin has been the accepted treatment for individuals with pulmonary emphysema due to alpha 1-antitrypsin deficiency. In addition, Prolastin has been used experimentally by inhalation for the treatment of cystic fibrosis. It has been administered with some success to treat the panniculitis associated with alpha 1-antitrypsin deficiency. As a greater number of severely impaired alpha 1-antitrypsin deficient patients receive lung transplantation, the role of Prolastin in the post-transplant therapy of these patients will need evaluation. Newer antiproteases may render Prolastin obsolete with respect to its route of administration and its pricing, however, the safety record of this drug has been impressive.