This report describes the results of an investigation conducted to assist EPA's New England Regional Office in evaluating vapor intrusion at 15 homes and one commercial building near the Raymark Superfund Site in Stratford, Connecticut. Methods were developed to sample sub-slab air and use basement and sub-slab air measurements to evaluate vapor intrusion on a building-by-building basis. A volatile organic compound (VOC) detected in basement air was considered due primarily to vapor intrusion if: (1) the VOC was detected in ground water or soil gas in the vicinity (e.g., 30 meters) of a building, and (2) statistical testing indicated equivalency between basement/sub-slab air concentration ratios of indicator VOCs and VOCs of interest. An indicator VOC was defined as a VOC detected in sub-slab air and known to be only associated with sub-surface contamination. Using this method of evaluation, VOCs detected in basement air due to vapor intrusion could easily be separated from numerous other halogenated and non-halogenated (e.g., petroleum hydrocarbons) VOCs present in basement air. As a matter of necessity, radon was used as an indicator compound at locations where an indicator VOC was not detected in basement air. However, when basement/sub-slab air concentration ratios were compared for radon and indicator VOCs, statistical non-equivalency occurred at three out of the four locations evaluated.