Performance testing was conducted on a Graseby Andersen 8-stage cascade impactor to evaluate it's accuracy. Performance testing was also conducted of a Graseby Andersen federal reference method(FRM) PM_2.5 sampler and an IMPROVE PM_2.5 sampler. These two samplers operate on very different principals; the FRM sampler uses jet impaction preseparators and the IMPROVE uses a cyclone preseparator. PM_2.5 concentrations as measured by the FRM and IMPROVE samplers as well as those determined by the Coulter Counter Multisizer from the TSP and PM₁₀ samplers, were not found to be significantly different, when statistically analyzed.