Increased proliferative activity determined in surgical specimens of hepatocellular carcinoma (HCC) has been associated with tumor grade and patient survival. The measurement of cell proliferation in echo-guided biopsies of small focal liver lesions might provide useful information for the early recognition of malignancy and for predicting the aggressiveness of small HCCs. We assessed the diagnostic and prognostic value of cell proliferation in 91 echo-guided needle biopsies of focal liver lesions using the monoclonal antibody Ki-67, which detects a human nuclear antigen that is present in proliferating cells. Measurements were performed by image cytometry as the percentage of Ki-67 positive hepatocytes nuclei over total hepatocyte nuclei in the biopsy. At the histological examination, 27 lesions were diagnosed as chronic hepatitis, 10 as cirrhosis, 11 as macroregenerative nodule, and 43 as HCC in cirrhotic liver. Although the highest Ki-67 values (> 20%) were found in less-differentiated HCCs, most well-differentiated HCCs and nine borderline nodules were completely devoid of Ki-67-positive hepatocytes. A sustained Ki-67 labeling (up to 16%) was found in hepatitis and cirrhosis, similar to that found in several malignant tumors. In the HCC subset, Ki-67 labeling was strongly correlated to the Edmondson-Steiner histological grade. However, survival analysis did not indicate a better outcome for those patients with low-proliferating tumors.