The histology of 72 livers from 72 children who underwent liver transplantation was reviewed. Nine children (12.5%) had hepatocellular carcinoma (HCC) and/or liver cell dysplasia (LCD) in their native livers. Ages at the time of transplantation ranged from 2 months to 11 years. Primary liver diseases included tyrosinemia (3), biliary atresia (2), chronic active hepatitis B (1), chronic active non-A non-B non-C hepatitis (1), idiopathic neonatal hepatitis (1), and neonatal iron storage disease (1). Explanted livers showed large multifocal HCC in two cases, incidental HCC in three, and dysplastic nodules in four. LCD also was present in three cases in conjunction with HCC. All patients had cirrhosis. Alpha-fetoprotein was measured in six children and was elevated in all six (range, 300 to 1,770,000 ng/mL; normal, 0 to 15 ng/mL). Abdominal computed tomography, ultrasonography, and/or magnetic resonance imaging showed large masses in two cases, but did not detect the tumors of less than 2 cm or the dysplastic nodules in the other seven children. After a follow-up period of 2 months to 3 years (mean, 19.8 +/- 12.1 months), eight children are alive and have no evidence of recurrence. The patient with neonatal iron storage disease died 2 months after transplantation, without evidence of tumor recurrence. The authors conclude that children with end-stage liver disease of diverse causes referred for liver transplantation may have LCD and/or HCC. Serial determination of alpha-fetoprotein and images studies may detect early lesions curable by liver transplantation.