A deficiency of the major serum alpha1-globulin, the alpha1-antitrypsin, was first described in five patients by Laurell and Eriksson in Sweden in 1963. It soon became obvious that severe alpha1-antitrypsin deficiency was familial, and highly associated with chronic lung disease, having its onset in the third or fourth decade of life. Since the early descriptions of this common deficiency state, it has become clearly associated with familial emphysema in some families, familial infantile cirrhosis in others, and occasionally with a combination of childhood lung and liver disease in siblings. For the pediatrician, severe alpha1-antitrypsin deficiency now enters into the differential diagnosis of both chronic pulmonary disease in childhood and obstructive jaundice in the newborn period; In addition, low levels of alpha1-antitrypsin in serum are characteristic of respiratory distress syndrome, and elevations of this protein may be found in a variety of clinical situations. The, alpha1-antitrypsin probably functions as a major control protein against the tissue-damaging effects of both endogenous and exogenous enzymes. This review will cover several basic and clinical features of this protein with respect to its importance in pediatrics.