The EPA is taking final action to revise the regulatory definition of volatile organic compounds (VOCs) for purposes of preparing state implementation plans (SIPs) to attain the national ambient air quality standards (NAAQS) for ozone under title I of the Clean Air Act (CAA). This final action adds trans 1-chloro-3,3,3- trifluoroprop-1-ene (also known as Solstice<SUP>TM</SUP> 1233zd(E)) to the list of compounds excluded from the regulatory definition of VOCs on the basis that this compound makes a negligible contribution to tropospheric ozone formation. As a result, if you are subject to certain federal regulations limiting emissions of VOCs, your emissions of Solstice<SUP>TM</SUP> 1233zd(E) may not be regulated for some purposes. This action may also affect whether Solstice<SUP>TM</SUP> 1233zd(E) is considered as a VOC for state regulatory purposes, depending on whether the state relies on the EPA's regulatory definition of VOCs. An exemption for Solstice<SUP>TM</SUP> 1233zd(E) was promulgated first as a direct final rulemaking but was withdrawn because EPA received an adverse comment.