Of 200,000 Swedish infants screened for alpha 1-antitrypsin deficiency (alpha 1 ATD), 184 (127 PiZ, 2 PiZ-, 54 PiSZ, and 1 PiS-) children have been followed prospectively, of whom 1 PiSZ and 5 PiZ children died in early childhood. We now report clinical and biochemical signs of liver disease in adolescence and the prognosis of neonatal liver disease up to the age of 18 years. The alpha 1 ATD subjects were offered a clinical checkup and liver tests at 16 and 18 years of age, 150 of 178 alpha 1ATD subjects undergoing checkups at age 16 and 166 at age 18. Liver tests were performed in 121 adolescents at both the 16- and 18-year checkups. None of the PiZ and PiSZ subjects checked at the age of 16 and 18 years had any clinical signs of liver disease. Abnormalities of serum alanine aminotransferase (S-ALAT) or gamma-glutamyl transferase (S-GT) were found at the 16-year checkup (all PiZ and PiSZ subjects tested included) in 17% of PiZ and 8% of PiSZ adolescents, and at the age of 18 years in 12% of PiZ and 15% of PiSZ subjects. In only two cases were both S-ALAT and S-GT concentrations abnormal at both the 16-year and 18-year follow-ups. Serum procollagen III peptide concentrations were normal in all those with abnormal liver test results. Of 127 PiZ subjects, 22 had manifested clinical signs of liver disease in infancy. Of these 22, two died early in life of cirrhosis.(ABSTRACT TRUNCATED AT 250 WORDS)