To evaluate the objective proliferative activity in HCC nuclear DNA contents were measured by means of microspectrophotometry and at the same time the immunohistochemical technique using anti-PCNA antibody was employed. Surgically resected 26 HCCs were analyzed in terms of cell proliferative activity and regional heterogeneity. The analysis was performed by immunohistochemical demonstration of PCNA and pathologic histochemical study in formalin-fixed, paraffin-embedded specimens and cytophotometric measurements of nuclear DNA contents in fresh specimens. The results were as follows. 1) Nine HCCs showed regional ploidy heterogeneity. 2) PCNA labeling index and histological grade of the marginal area was much higher than that of the central area. From these results, we concluded that in the process of the HCC progression proliferative activity was decreased in the central area and was not decreased in the marginal area.