International guidance documents relating to the use of laser diffraction, such as ISO133220:2009 and USP<429>, highlight the importance of using Certified Reference Materials to test the performance of laser diffraction systems during their lifetime. This is particularly important when laser diffraction is used as part of Quality Control operations or within audited laboratories, as testing using reference materials provides a baseline performance verification which provides assurance that any sample measurement variability relates to the product being tested rather than drift in the instrument performance.. The webinar will be presented by Dr Steve Ward-Smith, who is a member of the ISO TC24/SC4 Particle Characterization committee where he advises on future guidance relating to the use and verification of laser diffraction systems.