Recombinant adenovirus vectors have been used extensively to deliver foreign genes to a variety of cell types in vitro and in vivo. One problem with the use of adenovirus vectors has been the difficulty of constructing new vectors. In this review, we introduce not only a simple in vitro ligation method that is quick and efficient for generating new vectors, but also a method by which to construct vectors containing genetically modified fiber proteins for achieving targeted gene transfer and expression. The system described here should offer a powerful tool for the construction of recombinant adenovirus vectors for human gene therapy.