As required under section 503A of the Food, Drug, and Cosmetic Act (FD&C Act), FDA is developing a list of bulk drug substances that are not the subject of a United States Pharmacopeia or National Formulary monograph, or a component of an FDA-approved drug, that can be used to compound drug products eligible for the exemptions identified in that section (List). In fall 2016, we expect to publish an NPRM proposing the criteria for evaluating bulk drug substances for the List, identifying 10 substances nominated for the list and whether FDA proposes the substance be placed on the List. This proposed rule will identify 15-20 additional bulk drug substances nominated for the List and whether FDA proposes the substance be included on the List, or not included on the List.