Drift reduction agent has been defined in ASTM E1519-10 [ASTM E1519-10: Terminology Relating to Agricultural Tank Mix Adjuvants, Annual Book of ASTM Standards, ASTM International, West Conshohocken, PA, 2010] as “a material used in liquid spray mixtures to reduce driftable fines.” Driftable fines are defined as “the % volume of a spray droplet size distribution with a diameter less than 105 microns.” ASTM E609-10 [ASTM E609-10: Terminology Relating to Pesticides, Annual Book of ASTM Standards, ASTM International, West Conshohocken, PA, 2010] defines drift as “The physical movement of an agrochemical through the air at the time of application or soon thereafter to any non or off target site. Drift shall not include movement to non or off-target sites caused by erosion, migration, volatility or wind-blown soil particles that occur after application unless specifically advertised on the label.” Because there are many commercial tank mix adjuvants designed to reduce spray drift, ASTM established a standard test method to evaluate their effectiveness. ASTM E2798-11 [ASTM E2798-11: Characterization of Performance of Spray Drift Reduction Adjuvants for Ground Application, Annual Book of ASTM Standards, ASTM International, West Conshohocken, PA, 2011] provides guidelines for the measurement of parameters pertaining to the performance of drift-reduction adjuvants under simulated field application conditions. The measurements can be made in a wind tunnel or lab spray chamber to represent ground applications. The method describes the preparation, composition and test/application conditions for droplet size and driftable fines measurements. The U.S. Environmental Protection Agency has published a proposed protocol covering the implementation of spray drift reduction technologies in the field. The results of ASTM E2798 were compared to drift reduction simulated by AGDISP (Continuum Dynamics, Ewing, NJ) to see whether a correlation between the two test methods exists.