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A tight junction (TJ) protein, claudin-1 (CLDN1), was identified recently as a key factor for hepatitis C virus (HCV) entry. Here, we show that another TJ protein, occludin, is also required for HCV entry. Mutational study of CLDN1 revealed that its tight junctional distribution plays an important role in mediating viral entry. Together, these data support the model in which HCV enters liver cells from the TJ. Interestingly, HCV infection of Huh-7 hepatoma cells downregulated the expression of CLDN1 and occludin, preventing super-infection. The altered TJ protein expression may contribute to the morphological and functional changes observed in HCV-infected hepatocytes. Recently, considerable progress has been made in elucidat-ing the molecular mechanisms by which hepatitis C virus (HCV) infects human liver cells. The current accepted model of HCV infection is that virus particles associated with lipopro-teins, found circulating in the bloodstream, use glycosamino