In vivo bioluminescence imaging (BLI) is a powerful technology that gives information on biological processes in living animals over multiple time points. Importantly BLI can also yield anatomical localization of signal which can provide important information when performing biodistribution studies of different macromolecules. This is of particular interest for gene therapy vectors such as adeno-associated virus (AAV) vectors in which knowledge of in vivo gene expression profiles help characterize what target tissues or organs the vector may be useful for. It can also be utilized to assess novel vector systems for their ability to overcome specific in vivo barriers of effective gene therapy. Here we describe BLI of AAV-encoded firefly luciferase (Fluc) expression in mice after intravascular delivery. This protocol can be amended for use with different virus vectors (e.g., lentivirus, adenovirus) as well as nonviral gene delivery (e.g., plasmid DNA, liposomes).