Previous studies showed that patients with resectable multiploid hepatocellular carcinoma (HCC) had lower overall survival rate and higher recurrent rate than did those with diploid or single aneuploid tumors after hepatic resection. We describe in this study the establishment and characterization of cell lines derived from a single HCC nodule containing multiploid DNA distribution. Two human HCC cell lines, designated HAGS 2.1 and HAGS 2.2, were established by primary culture and single cell cloning methods from a patient with a multiploid HCC tumor. Both cell lines expressed bile canalicular domain-specific antigen of human hepatocyte. The HAGS 2.1 cells were spindle-shaped without prominent intracellular vesicles and had a doubling time of 38 h with DNA ploidy of 4.4 N; cells of HAGS 2.2 were polygonal with many intracellular vesicles and had a doubling time of around 42 h with DNA ploidy of 5.1 N. Hepatitis B surface antigen was detectable in HAGS 2.2 but negative in HAGS 2.1 cells. Both HAGS 2.1 and HAGS 2.2 expressed major histocompatibility complex (MHC) class I antigen, but the former expressed more MHC class II antigen than did the latter. Polymerase chain reaction and subsequent single strain conformation polymorphism analysis disclosed the presence of preS and S regions and the absence of C and X regions of HBV genome in cells of both HAGS 2.1 and HAGS 2.2. We conclude that the establishment of cell lines derived from a single HCC tumor containing multiploid DNA distribution might provide a good in vitro model to study the carcinogenesis and the recurrence mechanism of human hepatocellular carcinoma.