AIM: To detect the origin of hepatocellular carcinoma (HCC) recurring and attempt to propose a new recurrent mechanism.METHODS: Orthotopic liver allotransplantation was performed on male rats with HCC- induced by diethylnitrosamine using female donors. Metastatic tumors in transplanted livers were obtained. A DNA probe that exhibits specificity for the rat Y chromosome was generated by using a set of primers specific to murine srygene. In situhybridization (ISH) for Y chromosome was used to detected the origin of HCC recurring. Male HCC tissue was designed to be positive control. ISH on female tissue and using non-labeled with DIG probe was thought to be negative control. RESULTS: Positive marks were seen through ISH for Y chromosome in recurrent tumor tissue and positive control. No signal was detected in both negative controls. CONCLUSION: Recurrent HCC after liver transplantation originated from disseminated tumor cells in recipients. Extrahepatic cells homing into liver may be a new HCC recurrence mechanism. Likewise, it implicates that this mechanism is responsible for HCC recurring after hepatectomy.