The Environmental Protection Agency (EPA) is finalizing a rule under the Toxic Substances Control Act (TSCA) to address its obligations under TSCA for hexachlorobutadiene (HCBD) (CASRN 87-68-3), which EPA has determined meets the requirements for expedited action under TSCA. This final rule prohibits all manufacturing (including import), processing, and distribution in commerce of HCBD and HCBD- containing products or articles, recognizing that there is unintentional production of HCBD as a byproduct during the production of chlorinated solvents, and that results in distribution in commerce of a very limited subset of that byproduct for burning as a waste fuel. These requirements will impact the amount of HCBD that will be manufactured, processed, distributed in commerce, used or disposed, thus reducing the exposures to humans and the environment from those activities prohibited under this final rule.