A number of pathogens (both viruses and bacteria) cause respiratory disease in swine. Often the clinical signs of disease are similar for infected pigs. Therefore to accurately diagnose the cause, multiple tests must be performed on each sample. The ability to simultaneously detect the most important PRDC pathogens in three assays improves the efficiency and reduces the cost of diagnostic testing. In this project, three “multiplex” assays were developed for the detection of 1) PRRSV (both NA and EU strains) and SIV; 2) PCV-2 and M. hyopneumoniae; and 3) P. multocida and A. pleuropneumoniae. These assays were based on state-of-the-art “real-time” PCR methods that allow detection of the pathogen at the same time that quantification of pathogen loads is made. It was demonstrated that these assays had diagnostic sensitivity equal to or exceeding standard PCR methods and culture methods. Use of vacuum “manifolds” for sample extraction and electronic repeating pipettors was shown to improve the efficiency of sample preparation and analysis without effecting diagnostic sensitivity and accuracy. The actual laboratory-associated costs of performing an individual assay (with a single sample preparation and real-time RT-PCR performed in duplicate) was calculated to be $5.50 for RT-PCR and $2.61 for PCR, not including assessment of positive and negative control reactions.