Objectives: Gene therapy may provide a means of modifying factors that contribute to the development of pathologic processes in transplanted lungs. Experiments were designed to study the feasibility of adenovirus-mediated gene transfer by way of the airways to the transplanted lung. Methods: Orthotopic left lung transplantation (Lewis to Lewis rats) was performed on four groups of animals. 300 μl of adenovirus solution encoding for β- galactosidase was infused into the left bronchus of donor rats at viral concentrations of 108 pfu/ml (n = 5), 109 pfu/ml (n = 6), and 1010 pfu/ml (n = 6), and the lung was ventilated for 5 minutes. Controls (n = 6) received medium only. Seven days after transplantation, native and transduced, transplanted lungs were harvested. Sections of lung were fixed and stained with a solution of X-Gal (5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside) and staining was evaluated for distribution by cell type and intensity. Results: β-Galactosidase expression was absent in the control group and in the native lungs. Two of five lungs in the 108 group expressed β- galactosidase, but in a limited distribution and intensity. All six lungs in the 109 group and five of six lungs in the 1010 group expressed β- galactosidase. The distribution and intensity of β-galactosidase expression ranged from only a few cells staining per slide to up to 75%. Pneumocytes were the most frequently stained cell type followed by alveolar macrophages. Conclusions: Gene transfer to the transplanted lung via the bronchial route is feasible and offers a novel technique to modify pathologic processes in the transplanted lung.