This guidance provides information on how the FDA defines the types of changes to approved risk evaluation and mitigation strategies (REMS), how application holders should submit changes to an approved REMS, and how the FDA will process submissions from application holders for changes to REMS. Specifically, this guidance provides information, as described in section 505-1(h) of the Federal Food, Drug, and Cosmetic Act (FD&C Act), on what types of changes to REMS will be considered modifications of the REMS and what types of changes will be considered revisions of the REMS (changes that may be implemented following notification to the FDA). This guidance is issued pursuant to section 505-1(h)(2)(A)(ii), (iii), and (iv) of the FD&C Act and section 1132(c) of Public Law 112-144.