The EPA is finalizing revisions to the December 31, 2002 New Source Review (NSR) Improvement rules to change the requirements of the major NSR programs regarding the treatment of fugitive emissions. Specifically, this final rule requires that fugitive emissions be included in determining whether a physical or operational change results in a major modification only for sources in the source categories that have been designated through rulemaking pursuant to section 302(j) of the Clean Air Act (Act). Also, this action elaborates on guiding principles for determining fugitive emissions for purposes of NSR and title V permitting.