Benzo(a)pyrene is a persistent toxic substance whose presence in the environment is of concern due to impacts on wildlife and human health. The eight U.S Great Lakes states and the Canadian province of Ontario have been collaborating on a regional toxic air emissions inventory for the past 15 years. Following the publication of the 2002 inventory, these states and province conducted a specific assessment of the benzo(a)pyrene emissions within the inventory, including the coverage of sources, estimation methods, available emission factors, errors and inconsistencies. Updates were made to the data to produce a regional inventory with greater accuracy, consistency and comprehensiveness. This report details the emissions inventory assessment process, presents the revisions to the 2002 regional benzo(a)pyrene emissions inventory, and offers recommendations for further correcting gaps in the emissions estimation for a variety of emission sources.