Abstract: To elucidate the impact of an infection with the recently discovered GB virus C (GBV-C) on the clinical course after orthotopic liver transplantation (OLT), we studied eight patients who were GBV-C RNA positive after transplantation. Five individuals had been viraemic before transplantation, three became GBV-C RNA positive thereafter. A control group comprised eight patients without pre- or post-transplant GBV-C infection. GBV-C RNA was detected by reverse-transcription followed by nested polymerase-chain-reaction (PCR) with primers corresponding to the NS5 genome region. Nested PCR products were sequenced directly. The five patients infected with GBV-C before transplantation remained GBV-C RNA positive throughout the time of observation. Pre- and post-transplant GBV-C RNA titres were almost identical. Phylogenetic analysis revealed a very close relationship between the pre- and post-transplant viral nucleotide sequences indicating persistent GBV-C infection. No signs of hepatitis could be detected after transplantation in all GBV-C infected patients. However, four out of eight GBV-C RNA positive patients had a clinical course complicated by severe cholestasis, which was not observed in the control group. Although GBV-C infection does not lead to an increase in the rate of post-transplant hepatitis, it might be associated with severe unexplained cholestatic courses after OLT.