A morphometric method was applied to measure the size, number, and surface membranes of the mitochondria in cells obtained from hepatitis B-associated hepatocellular carcinoma (HCC), from cirrhotic portions of livers with and without HCC, and from alcoholic liver disease (ALD). The mitochondria in HCC cells showed a significantly higher numerical density and surface density of internal membranes and cristae than mitochondria in cirrhosis and ALD. The findings suggest an increased functional activity of mitochondria in HCC.