Four methods for evaluating the dustiness of powders have been compared. The relatively new UNC Dustiness Tester first described by Boundy et al. (2006) in the Annals of Occupational Hygiene, which was developed specifically for the measurement of hazardous and/or highly potent substances, a single-drop device, a rotating-drum method, and a continuous drop-down apparatus. The four methods show four different ratings of dustiness for nine reference materials. This article describes the differences, explores reasons for the deviations, identifies a need for distinct dustiness test methods, and highlights the significance for occupational health and safety.