CEPA requires the ministers of the Environment and of National Health and Welfare to prepare and publish a Priority Substances List that identifies substances, including chemicals, groups of chemicals, effluents and wastes that may be harmful to the environment or constitute a danger to human health. The assessment of whether hexachlorobenzene is toxic, as interpreted in CEPA, was based on the determination of whether it enters or likely enters the Canadian environment in a concentration or quantities or under conditions that could lead to exposure of humans or other biota at levels that could cause adverse effects. In this report, an overview of the findings is presented. An extended summary of technical information critical to the assessment is presented in Section 2. The assessment of whether HCB is toxic under CEPA is presented in Section 3.