Six hundred commercial crossbred piglets were experimentally infected with the Porcine Reproductive and Respiratory Syndrome (PRRS) virus. Blood samples and body weights were collected at least once per week throughout the 6-week test period. Blood samples were used to measure the degree of infection through viral load. Body weight was measured to look at the impact of the PRRS virus on growth. Serum viral load from day 0 to 21 were summarized by area under the curve. Heritability for viral load and weight gain from 0 to 42 days after infection was 0.28 and 0.26, respectively. All piglets were genotyped for over 60,000 genetic markers comprising single nucleotide polymorphisms (SNPs) distributed across the genome. Regions on chromosomes 3, 4, and X appeared to be associated with area under the curve, while regions on chromosomes 1, 4, 7, and 17 appeared to be associated with weight gain. These results are promising to the swine industry, as it shows that there is genetic variation for resistance to PRRS within a population and that selection for resistance or susceptibility to the virus is plausible.