The chapter provides information needed to ensure that sampling and data analysis are well done. It discusses sampling and analysis associated with mass tests using EPA Test Methods 5 and 17 and particle size distribution tests conducted with cascade impactors. All steps in the sampling and data analysis process are covered. Considerably more space is given to cascade impactors than to EPA Test Method 5, mainly because cascade impactors are more difficult to use and data reduction is difficult. Computer programs for reducing mass train and cascade impactor data are presented, along with quality control recommendations.