The main objective of this study is to evaluate the performance of candidate sampling methods for potential use as a Federal Reference Method (FRM) capable of providing an estimate of coarse particle (PMc: particulate matter with an aerodynamic diameter between 2.5 um and 10 um) mass concentrations in ambient air. Five sampling approaches are being evaluated. These approaches include a discrete method for measuring coarse particles directly using a commercial sequential dichotomous sampler; and a discrete difference method, which uses two commercial FRM samplers, one to measure PM2.5 the other PM10 with the difference, PM10-PM2.5, representing an estimate of PMc. Filters from these two sampler types are analyzed gravimetrically. The study also evaluates two continuous coarse particle samplers which measure PMc directly with a time resolution of one hour: one a commercial automated dichot and the other a prototype dichot that measures PMc directly. The direct sequential and continuous dichotomous methods use a virtual impactor for separating fine and coarse particles. The final PMc sampler is an aerodynamic particle sizer which measures aerosol size distribution then uses the collected data to estimate the PMc mass concentration. The samplers will be evaluated in three locations that provide diverse challenges to the samplers, including high PMc to PM10, high PM2.5 to PM10, and a site impacted by high and low values under cold conditions. This work has been funded in part by the United States Environmental Protection Agency under contract number 68-D-00-206 to ManTech Environmental Technology, Inc. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.