Fifty-nine patients (median age 6.0 years) with liver disease and ten healthy children without liver disease (median age 7.5 years) had serial measurements of functional residual capacity (FRC) over a period of at least 6 months. Twenty-eight children with alpha-1-antitrypsin deficiency (A1ATD) tended to have higher lung volumes than 26 with extrahepatic biliary atresia (EHBA). Fifteen children had persistent hyperinflation (FRC greater than 120% predicted for height; 2 SD above the mean of controls); in five children (four with A1ATD) this was unresponsive to bronchodilator therapy. Two of the children with A1ATD who had persistent unresponsive hyperinflation on three serial measurements were only 3 and 4 years of age. No healthy child without liver disease was hyperinflated. These results suggest that A1ATD may be associated with lung function abnormalities even in very young children.