Cytokines are small secreted proteins which mediate and regulate immunity to viral infections in swine and other species.  Evidence suggests that PRRSV does not induce early, effective cytokine responses in the pig leading to clinical disease and viral persistence. The immune response to PRRSV occurs late in infection and is weak in comparison to the response to other swine viruses.  In designing second generation PRRSV vaccines, it would be very useful to have rapid, standardized assays available to measure whether these vaccines, or viral proteins proposed to be used in the vaccines, are inducing more rapid and protective cytokine responses. The assay should also prove useful for measuring cytokines that could determine genetic resistance to PRRSV and immune responses to other swine pathogens. The objective of this study was to develop an assay to simultaneously quantify 8 porcine cytokines in serum using Luminex xMap™ technology.  A multiplex assay was optimized to detect innate inflammatory (IL-1 β, IL-8, IFN-α, TNF-α, IL-12); regulatory (IL-10), Th1 (IFN-γ) and Th2 (IL-4) cytokines. The assay was optimized, compared to individual cytokine tests and used to measure cytokines in a PRRSV vaccine study. The study showed high levels of IL-12 in pigs vaccinated and challenged with PRRSV, but this high level did not correlate with protection. This study is the first describing the development of a well validated 8-plex fluorescent microsphere immunoassay (FMIA) for the detection of swine cytokines in serum.