Twenty-three hepatoblastomas of childhood, sixty-two adult hepatocellular carcinomas, and two hepatic sarcomas were examined immunohistochemically with the use of a polyclonal antibody against rat liver fatty acid-binding protein (L-FABP), which cross-reacts to human L-FABP. All the hepatoblastomas and half of the hepatic cell carcinomas contained L-FABP immunoreactive tumour cells, whereas two hepatic sarcomas were negative. The overall frequency of immunostained tumour cells was 43.5 per cent in hepatoblastomas and 18.6 per cent in hepatocellular carcinomas, respectively. Histologically well-differentiated areas contained more numerous immunopositive cells than undifferentiated or immature ones. These results indicate that L-FABP immunoreactivity is a new candidate for a tumour cell marker in hepatic cell malignancies, although its biological role has not been elucidated.