Several genetic events are necessary for a cell to become malignant. Some of these events are activations of protooncogenes and loss of normal functions of tumor suppressor genes. Recently loss of heterozygosity at specific loci on some chromosomes have been observed in several tumors. Loss of heterozygosity in the tumor suggests that a certain tumor suppressor gene may reside near the locus of the probe by which the loss of heterozygosity was demonstrated. In hepatocellular carcinoma, loss of heterozygosity on chromosome 1p, 4q, 5q, 10q, 11p, 13q, 16q, 17p and 22q are observed. Inactivation of tumor suppressor genes on these chromosomes may play important roles in tumorigenesis or progression of hepatocellular carcinoma.