Hybridomas producing human monoclonal antibodies (HMAbs) against varicella-zoster virus (VZV) were generated by fusing murine myeloma cells with human lymphocytes immunized in vitro. An assay system was developed to select anti-glycoprotein (gp)III HMAbs from the pool of anti-VZV HMAbs. A murine anti-gpIII MAb, 4B7, did not react with a VZV-infected cell homogenate, but did react with a VZV-infected cell monolayer, whereas anti-gpI and anti-gpII MAbs reacted with both antigens. Hybridomas were screened to obtain HMAbs having a reaction profile similar to that of 4B7 and one such clone, V3, stably produces human IgG1 (kappa). HMAb V3 immunoprecipitated a VZV antigen of 115K to 120K, which was not immunoabsorbed by an anti-gpII HMAb, implying that V3 recognizes gpIII. V3 neutralized VZV independently of complement, unlike anti-gpI and anti-gpII HMAbs. All five strains of VZV tested were completely neutralized by V3, and the dose of V3 required to reduce the number of virus plaques by 50% ranged from 0.027 to 0.15 micrograms/ml. V3 was also able to inhibit the spread of virus infection from infected to uninfected cells, whereas anti-gpI and anti-gpII HMAbs could not. In addition, V3 mediated antibody-dependent cellular cytotoxicity but not complement-dependent cytotoxicity of VZV-infected cells. The results suggest that an anti-gpIII HMAb may provide a new means of passive immunoprophylaxis and also help to identify an antigenic epitope appropriate for a subunit vaccine.