Adenoviruses have double-stranded DNA genomes, have demonstrated promise in preclinical models [12, 13] and are well tolerated at low to intermediate doses in humans [14, 15] . Advantages include their ease of production, the high effi ciency at which they can infect the pulmonary epithelium [14, 16] and that they can deliver relatively large transgenes. A disadvantage of adenoviruses is their immunogenicity, particularly in repeated doses [14] . Newer adenoviral vectors, in which much of the immuno genicity has been removed, hold promise [17] . While adenovirus-mediated gene transfer in the absence of epithelial damage is relatively ineffi cient [18] , this may be less of a problem in ALI/ARDS that is characterized by widespread epithelial damage.