Viral vectors are the most eff ective and effi cient way of getting larger nucleic acid sequences, particularly genes, into cells (Table 1) . Th e viral genome is modifi ed to remove the parts necessary for viral replication. Th is segment is then replaced with the gene of interesttermed a transgene -coupled to a promoter that drives its expression. Th e modifi ed genome is then encapsulated with viral proteins. Following delivery to the target site, the virus binds to the host cell, enters the cytoplasm and releases its payload into the nucleus (Figure 1 ). Th e size of trans gene that can be used depends on the capsid size. A number of diff erent viral vectors have been used in preclinical lung injury studies to date.