We used a replication defective human lentiviral (HIV) vector encoding the lacZ cDNA and pseudotyped with the vesicular stomatitis virus (VSV) glycoprotein (G) to evaluate the utility of this vector system in airway epithelia. In initial studies, apical application of vector to polarized well differentiated human airway epithelial cell cultures produced minimal levels of transgene expression whereas basolateral application of vector enhanced levels of transduction approximately 30-fold. Direct in vivo delivery of HIV vectors to the nasal epithelium and tracheas of mice failed to mediate gene transfer, but injury with sulfur dioxide (SO 2) before vector delivery enhanced gene transfer efficiency to the nasal epithelium of both mice and rats. SO 2 injury also enhanced HIV vector-mediated gene transfer to the tracheas of rodents. These data suggest that SO 2 injury increases access of vector to basal cells and/or the basolateral membrane of airway surface epithelial cells. Quantification of gene transfer efficiency in murine tracheas demonstrated that transduction was more efficient when vector was delivered on the day of exposure (7.0%, n= 4) than when vector was delivered on the day after SO 2 exposure (1.7%, n= 4).