Clinicopathological analyses were performed on 11 cases of juvenile (less than 40 years) hepatocellular carcinomas (HCC) and compared with those of 187 cases of nonjuvenile HCCs. 91% of juvenile HCC cases were positive for HBsAg in their sera and it was much higher than that of nonjuvenile group (p less than 0.05). Familial clustering of HBV carriers or advanced liver diseases was found in 50%. 73% of juvenile HCC cases had cirrhosis. Abdominal pain was found most frequently as initial symptom. All except one case, who had surgical resection of the tumor, were rapidly fatal. Interestingly the association of paraneoplastic syndrome (PNS) was more frequently seen in juvenile HCC cases (36.3%) than in nonjuvenile HCC ones (5.9%, p less than 0.05). In juvenile HCC cases with PNS, LC was less associated, serum alphafetoprotein tested higher and prognosis was worse than those without PNS. Therefore, these results imply that HBV plays an important role for the development of juvenile HCC and juvenile HCC patients with PNS show characteristic features in HCC patients in Japan.