The U.S. Food and Drug Administration (FDA) has issued a draft revision of Guidance for Industry (GFI) #170: Animal Drug User Fees and Fee Waivers and Reductions. This guidance describes the fees the agency is authorized to collect under the Animal Drug User Fee Act of 2003 (ADUFA), as amended, the information the FDA recommends sponsors submit in support of a request for a fee waiver or reduction, how to submit such a request, and the FDA’s process for reviewing these requests. This draft revision of the guidance clarifies the criteria for Barrier to Innovation waivers, clarifies the procedures for Small Business waivers, and makes additional clarifying changes.