During 1972-1974, 200,000 Swedish infants were screened for alpha 1-antitrypsin deficiency. Of 127 PiZ (Protease inhibitor) children followed from infancy to 12 years of age, four PiZ children with neonatal liver disease have died; two of liver cirrhosis, one was found to have liver cirrhosis at autopsy, having died of aplastic anemia and the fourth died in an accident. Liver microscopy showed a mild increase of periportal fibrous tissue. Another PiZ child died of anaphylactic shock. At 12 years of age, none of the PiZ children have clinical symptoms of liver disease. No PiZ-, PiSZ, PiS- or PiFZ child has had any clinical symptom of liver disease. One PiSZ child died of sudden infant death syndrome. Laboratory analyses from birth through 12 years of age have shown increased S-Bilirubin levels in 11% of the PiZ infants, which normalized within the first half year of life. S-GT was abnormal in about half of the infants, but had normalized when checked at 8 and 12 years of age in all but 6-3% of the PiZ children. The percentage of abnormal S-ALAT test results have decreased from 73% during the first year of life, to about 15% at the age of 12. The range of the abnormal levels also decreased considerably. Abnormal S-GT or S-ALAT levels were found in about 20% of the PiSZ infants, the proportion decreasing to 2% at the age of 12.