Porcine reproductive and respiratory syndrome (PRRS) virus imposes devastating effects on swine health and productivity. In the U.S., PRRS virus causes approximately $560 million in losses each year. Vaccination of animals is one way to reduce losses from infectious diseases including PRRS. Current modified live and killed vaccines have some success, although differentiation between vaccinated and infected animals has been a problem. In addition, live attenuated vaccines have resulted in appearance of PRRS like symptoms in sow herds and altering semen quality of boars. As such, new approaches are being utilized to develop better PRRS vaccine. Using harmless porcine adenovirus 3 (which infects respiratory tract of pigs), we have constructed recombinant porcine adenovirus 3 expressing vaccine antigens genes (synthesized in the laboratory for increased expression) of PRRS virus. These recombinant PAV-3s will be used to evaluate their ability to induce a protective immune responses in pigs against PRRS virus challenge. The advantages of our approach of using harmless PAV-3 to deliver PRRS vaccine antigens to pigs is that such vaccines are safe, cost-effective, and highly efficacious.