An advantage of gene-based strategies is the ability to target specifi c cells within an organ; for example, the epithelial cells of the lung. Novel nebulization technologies, which facilitate the delivery of large quantities of undamaged vector to the distal lung, demonstrate considerable promise in this regard [9] . Alternative approaches to spatial targeting include targeting specifi c receptors that are plentiful on the target cell to increase transfection effi ciency. An interesting development in this regard is the targeting of systemically administered therapies to the pulmonary endothelium using antibodies to proteins expressed preferentially on these cells ( Figure 5 ) [10] . In these studies, the antioxidant enzyme catalase was conjugated with antibodies to the adhesion molecule PECAM, which is widely expressed on pulmonary endothelial cells, and to a nonspecifi c IgG antibody. Th e anti-PECAM/catalase conjugate, but not the IgG/catalase conjugate, bound specifi cally to the pulmonary endothelium and attenuated hydrogen peroxide injury.