The economic losses caused by Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) infection are estimated to cost the US swine industry more than $640 million annually (USDA, 2008). While significant advances have been made through research efforts to enhance our understanding of PRRSV at the animal health, immunological and genomic level, this disease still remains a significant issue in the US swine industry. Although we clearly know that PRRSV attenuates ADG of production pigs, its direct impact on feed efficiency, nutrient and energy digestibility, and whole body lean and fat accretion in grow finisher pigs has been poorly characterized. Therefore, the overall objective of this project was to characterize the impact PRRSV challenge has on grow-finisher pig feed efficiency, energy and nutrient digestibility, and tissue accretion rates.