Advanced head and neck squamous cell carcinomas (HNSCCs) have a poor prognosis despite aggressive multimodal therapy. The goal of our study was to test the feasibility of gene transduction as a novel therapy for head and neck cancer. Three human HNSCC cell lines were transduced in vitro with a replication-deficient recombinant adenovirus containing the lacZ marker gene (Ad2/CMV beta gal). Gene transduction efficiency was dependent on multiplicity of infection, duration of exposure to the virus, and viral concentration. Next, the HEp-2 cell line was transduced with an adenoviral vector (Ad.RSVtk) containing the herpes simplex virus thymidine kinase (HSVtk) gene, which, when expressed, sensitizes transduced cells to ganciclovir (GCV). Subsequent administration of GCV resulted in complete tumor cell killing. These results suggest that adenovirus-mediated transfer of HSVtk and administration of GCV has potential as a new therapy for HNSCC.