As required under section 6(b)(1) of the Toxic Substances Control Act (TSCA), EPA is issuing a final rule that establishes the process and criteria that EPA will use to identify chemical substances as either High-Priority Substances for risk evaluation, or Low-Priority Substances for which risk evaluations are not warranted at the time. The final rule describes the processes for formally initiating the prioritization process on a selected candidate, providing opportunities for public comment, screening the candidate against certain criteria, and proposing and finalizing designations of priority. Prioritization is the initial step in a new process of existing chemical substance review and risk management activity established under TSCA.