Purpose. To determine whether a reporter gene can be introduced into adult mammalian corneal endothelial and trabecular meshwork cells in vivo using a recombinant replication deficient adenovirus. Methods. Purified replication- deficient adenovirus containing the cytomegalovirus-promoted Escherichia coli reporter gene, LacZ was injected into the vitreous cavities or anterior chambers of 30 adult CD-1 mice using the contralateral eyes as controls. LacZ expression was assessed histochemically in enucleated eyes from 2 to 21 days after injection using the Å-Galactosidase (β-Gal) assay. Results. LacZ expression was demonstrated in corneal endothelial anti trabecular meshwork cells for as long as 14 days after injection. β-Gal activity was also observed in lens and iris epithelial cells. There was no toxicity of the adenoviral vector demonstrated histologically, and no nonocular tissues expressed lacZ as measured by β-Gal assay. Conclusions. A functional gene call be transferred in vivo into adult mammalian corneal endothelial and trabecular meshwork cells using a replication-defective adenoviral vector. Gene expression is relatively short-lived compared to that demonstrated previously in other ocular tissues (photoreceptors and retinal pigment epithelium). Adenoviral vectors may be a viable means for short-term delivery of therapeutic genes in vivo to cells in the anterior segment of the eye.