To evaluate the effect of preoperative treatment on proliferative activity and prognosis of the hepatocellular carcinomas(HCCs), fifty-three surgically resected HCCs were studied. Twenty cases were treated preoperatively and thirty-three were not treated before surgery. The proliferation index(PI, % of proliferating cell nuclear antigen positive cells) of the remaining cancer cells following pretreatment was 27.39, which was slightly lower than that of not-pretreated cases(35.41). Although PI was similar among gross types and among histologic grades, tumors of the expanding type and of the histologic grade I revealed distinctly low PI in pretreated cases. Two-year survival rate was not significantly different between pretreated and not-pretreated cases(67.4 vs 52.7). But the differences between gross types(p<0.05) and between histologic grades(p<0.01) were significant. Total necrosis of tumor occurred in five pretreated patients, all of whom were alive during two-year follow-up. Smaller HCCs showed better prognosis(p<0.01). Although PI appeared not correlated well with the two year survival rate, the pretreated HCCs with low PI showed better survival than those with high PI(p<0.05). The results indicate that preoperative modalities induce tumor necrosis, but do not reduce the proliferative activity of tumor cells significantly, and that pretreatment does not affect the long-term prognosis of HCCs except for the occasions of total necrosis of tumor.