Short-term cultures of three primary hepatocellular carcinomas were cytogenetically analyzed. Case 1 displayed a normal karyotype. Case 2 had, in addition to cells with a normal male chromosome complement, a clone with -Y. In case 3, two abnormal clones were found, one with -Y and one with a highly aberrant karyotype: [formula: see text] Our results, collated with the findings in one previously published primary hepatocellular carcinoma and in three cell lines, suggest that structural changes of chromosomes 1 and 6, leading to loss of 1p and 6q material, and loss of chromosome 16 are frequent events in hepatocellular carcinogenesis.