To investigate cumulative genetic changes during development and progression of hepatocellular carcinoma (HCC), we examined DNAs isolated from 104 tumors for loss of heterozygosity (LOH) at 13 loci on six chromosomal arms and for an increase of copy number ("multiplication") of alleles on 8q, using polymorphic microsatellite markers. A comparison of genetic features with clinicopathological stages of these tumors revealed that LOH on 1p had occurred in tumors at an early stage or with a well-differentiated histological phenotype (8/26; 31%) as well as in tumors at more advanced stages. Genetic alterations on chromosome arms 4q, 8p, 8q, 13q, 16q, and 17p were more often observed in tumors of more advanced stages and poorer differentiation grades. When size was the criterion for comparison, LOH on 1p was observed frequently even in tumors smaller than 2 cm (6/16; 38%), whereas allelic losses on 16q were detected frequently only in larger tumors. These results suggest that the putative tumor suppressor gene(s) assumed to be located on 1p may be involved in an early step of carcinogenesis in liver tissue and that the other genetic alterations examined here may play important roles in progression of HCC.