Hepatocellular carcinoma (HCC) is one of the most frequent malignancies worldwide, showing the highest prevalence in Asia and Africa; it is the second most common form of lethal cancer after gastric cancer in China, and the third most common after gastric and lung cancers in Japan. Mutational activation of Ras family oncogenes and amplification of the Myc gene have been considered to be significant events in the process of experimental hepatocarcinogenesis in many animal models. Many investigators have performed allelotype analysis on HCCs in an attempt to localize tumor suppressor loci. Human carcinogenesis is a multistep process in which many genetic or epigenetic alterations contribute to each stage of development and progression. DNA hypermethylation at D17S5 was detected in 90% of the HCC tissues and 44% of the liver tissues showing chronic hepatitis or cirrhosis, but was not demonstrated in normal liver tissues. Cancer recurrence after surgery is one of the major obstacles which hinders the curability of HCC.