ObjecUve To iovestigate the role of hepatitis C virus (HCV) in the malignant transformation of bile duct celle. Tissues from 6Chinese patients and 6 American patients wtiJl cholengienarcinoma were studied. Mammals RNA was extracted from the selected tumor areas eq formalin-fixed, paraffin embedded sections, followed by reverse transcription double polymerase chain reaction (RT-PCR) and Southern blotting. Results Positive and negative strand HCV RNA sequences were detected in seven out of tweive patients witn choiangiocarcinorna. A high positive rate was found in Chinese patients (83%) as compared to US patients (38%). Coaclualon Our finding suggests HCV may play a role in the malignent transformation of bile duct cells.