The Pennsylvania Department of Environmental Protection (PADEP) is in the process of overhauling Pennsylvania’s current vapor intrusion guidance document issued 2004. PADEP, in conjunction with the Cleanup Standards Scientific Advisory Board (CSSAB), has been evaluating changes in the manner in which vapor intrusion issues have been addressed over the past decade and the evolving science associated with vapor intrusion. PADEP issued a new vapor intrusion guidance document in proposed form on July 25, 2015. The public comment period regarding the proposed vapor intrusion guidance document closed on September 23, 2015. The proposed vapor intrusion guidance document makes fundamental changes in the way that vapor intrusion issues are currently being handled. In general terms, criteria associated with vapor intrusion are more stringent and the options for addressing vapor intrusion are more limited under the proposed vapor intrusion guidance. The proposed vapor intrusion guidance is expected to be finalized in 2016 and will have important ramifications for sites where volatile regulated substances are present.