To analyze cytomorphologic characteristics of hepatoblastoma (HB) and evaluate the feasibility of recognizing its histologic subtypes in smears. Fine needle aspirates from 14 primary and 1 metastatic HB were reexamined. The diagnosis of HB was confirmed by tissue examination (10 cases) and by clinical and laboratory findings alone (5 cases). In 12 samples, neoplastic cells resembled immature hepatocytes but were smaller and had a higher nuclear/cytoplasmic ratio. In nine of these smears the cells were rather uniform, while the other three presented with moderate pleomorphism. The cells were arranged in three-dimensional clusters, loose sheets, cords, rosettelike structures and occasional pseudopapillae and were dispersed. With knowledge of the cellular features and architectural patterns of HB, a reliable diagnosis could be obtained in 12/15 cases without the use of special techniques. In the remaining three aspirates the tumor cell population partly or entirely differed from normal hepatocytes, requiring ancillary techniques for proper diagnosis. On reexamination of the 10 cases with tissue diagnoses, 4/6 mixed HBs could be correctly subtyped, whereas the distinction between embryonal and fetal cells in four cases of epithelial HB seemed questionable.