By cloning from cultivation in vitro of a human hepatoblastoma 3 epithelial cell lines were established, all of which produced alpha-fetoprotein and one of which did albumin in culture. Observation with electron microscopy demonstrated desmosomes and glycogen granules in the cytoplasm of these cells. The morphology, growth characteristics, alpha-fetoprotein production, heterotransplantability, and karyology of the cloned cells suggested that these clonal lines were derived from the tumor cells and retained their malignant characteristics.