Human herpesvirus-8 (HHV-8) is implicated in the pathogenesis of Kaposi's sarcoma. HHV-8 envelope glycoprotein B possesses the RGD motif known to interact with integrin molecules, and HHV-8 infectivity was inhibited by RGD peptides, antibodies against RGD-dependent α3 and β1 integrins, and by soluble α3β1 integrin. Expression of human α3 integrin increased the infectivity of virus for Chinese hamster ovary cells. Anti-gB antibodies immunoprecipitated the virus-α3 and -β1 complexes, and virus binding studies suggest a role for α3β1 in HHV-8 entry. Further, HHV-8 infection induced the integrin-mediated activation of focal adhesion kinase (FAK). These findings implicate a role for α3β1 integrin and the associated signaling pathways in HHV-8 entry into the target cells.