In order to elucidate the biologic behavior of hepatocellular carcinoma (HCC), the long-term prognostic impact of the pathologic features of 143 surgically resected HCC were studied. Seventy-four were smaller than 5 cm in diameter (small HCC), and 69 were larger (large HCC). This study confirmed that tumor size was an important but not the only determining prognostic factor in HCC. Although cirrhosis could cause hepatic failure, patient mortality was mainly attributable to tumor recurrence, which, in turn, was strongly correlated with the invasive nature of HCC. Tumor invasion to the liver and the intraportal spread were very frequent and particularly extensive in large HCC. In both small and large HCC the noninvasive groups not only had high 4-year actuarial survival (84.6% and 90%, respectively), but there was also no patient mortality from intrahepatic tumor recurrence. Therefore, it was concluded that invasiveness of an HCC is the most crucial factor in determining the long-term outcome for the patient, and that the clinical course of resected HCC is predictable in a great majority of the cases. In our small HCC series only 2.4% of HCC were regarded as having true multicentric origin. These findings suggest that the majority of HCC occur unicentrically, and that multiplicity and tumor recurrence result mostly from intrahepatic dissemination. In both small and large HCCs invasive tumors were accompanied by high patient mortality from tumor recurrence even when the tumor was small, indicating that intrahepatic spread may start very early during the growth of HCC.