FDA issued the first in a series of guidance documents intended to bolster the security of the nation’s drug supply. The guidance document, entitled Guidance for Industry on Standards for Securing the Drug Supply Chain—Standardized Numerical Identification for Prescription Drug Packages,” aims to assist with the development of standards and systems for identification, validation, authentication, and tracking and tracing of prescription drugs at the package level; that is, the smallest unit placed into interstate commerce by the manufacturer or the repackager for individual sale to the pharmacy or other dispensers of the drug product. The guidance document discusses what number (e.g., serialized National Drug Code or sNDC) should be used as the standardized numerical identifier (SNI) for certain products, what this identifier should include, and why FDA chose particular SNIs for different types of products.