A series of particulate emission tests were conducted on commercial cotton gins in New Mexico and California. All measured exhausts used high efficiency cyclones as emission control devices. In another series of tests, seed cotton from producers in Alabama, Arizona, Arkansas, California, Georgia, Mississippi, Missouri, New Mexico, South Carolina, Tennessee, and Texas was ginned at either the Stoneville or Mesilla Park USDA, ARS Cotton Ginning Laboratories. Particulate emissions during ginning were sampled from the exhausts of the unloading separator and the first lint cleaner. For the commercial gin particulate emission test, total suspended particulate (TSP) for all gins averaged between 0.069 and 0.092 g/m³ (0.03 and 0.04 grains per dry standard cubic foot (gr/dscf)) of air emitted at the cyclone. The PM10 fraction of the TSP ranged between 35 and 69% depending on the method of determination and PM2.5 was determined to be between 0.4 and 2.5% of TSP (measured by Coulter Counter). Opacity readings did not correlate with measured TSP. The Hand-held Aerosol Monitor (HAM) correlates well with PM10 levels as determined by the Coulter Counter.