This report describes the clinical, biochemical, and hepatic morphologic findings in ten children with severe serum alpha1-antitrypsin deficiency. Genetic protease inhibitor (Pi) phenotyping, using acid-starch gel and crossed antigen-antibody electrophoresis, demonstrated Pi phenotype ZZ in all our cases. In eight patients, manifestations of liver disease appeared during the first year of life. The case reports show that alpha1-antitrypsin deficiency should be suspected in any child with neonatal hepatitis, unexplained hepatomegaly or splenomegaly, or cirrhosis. In our report, one infant is normal at age 6 months, and one infant had progressive hepatic damage that culminated in liver failure and death at age 6 months. The variable clinical course and prognosis for infants with severe alpha1-antitrypsin deficiency is well illustrated by these two infants.