Adenoviruses can efficiently induce immunity in the lung following single enteric delivery. These viruses can also be engineered to express a number of heterologous proteins in vitro. In the past 10 years, recombinant adenoviruses expressing a variety of antigens have been constructed and tested. This article reviews the main properties of adenoviruses which render them attractive for vaccine development, as well as the results of the immunization studies performed to date. Some disadvantages of this technology and the desired characteristics of second generation adenoviral vectors are discussed.