Highly polar organic compounds (HPOC) are important atmospheric constituents due to their ability to attract water and thus act as cloud condensation nuclei (CCN). HPOC are defined here as those soluble in methanol or having a polarity index of up to 6.6 on the Snyder scale. All HPOC are fully soluble in water, and the dominant chemical species present in PM2.5 also are found in atmospheric cloud water (Sagona et al., 2010). A greater understanding of chemical types and the seasonal and spatial concentrations of HPOC in PM2.5 could help identify the transformations and fate of these species in urban atmospheres in the northeastern U.S. The Speciation of Organics for Apportionment of PM2.5 (SOAP) project was a two-part campaign to collect aerosol samples in the NY megacity region. The first campaign (SOAP 2002-2003) operated from May 2002 to May 2003 and followed the 1-in-3 day sampling schedule prescribed by the U.S. EPA Speciation Trends Network (STN) federal air monitoring protocol. The SOAP 2002-2003 sites were located at existing air quality monitoring sites operated by NY, NJ and CT. Sites were selected so that simultaneous mass and total organic and elemental carbon concentrations were available from the STN monitoring program. The four SOAP 2002-2003 sites included the principal U.S. EPA supersite in New York City in Queens, NY; an urban site in Elizabeth, NJ that generally was upwind of the supersite; a suburban site in Westport, CT that usually was downwind of the supersite and was within 1 km of Long Island Sound; and a regional background site in Chester, NJ. The second campaign (SOAP-NY) operated on a 1-in-6 day STN sampling schedule from September 2005 through February 2007. SOAP-NY collocated measurements were available from federal PM2.5 monitoring programs at the Pinnacle, NY and Bronx, NY locations. SOAP PM2.5 sample filters, travel and dynamic blanks were measured for elemental (EC), organic (OC) and total carbon (TC) using the NIOSH Method 5040. PM2.5 mass was obtained from the NY, NJ, and CT state air quality monitoring agencies. HPOC were isolated through Soxhlet solvent extraction using methanol. 107 PM2.5 filter composites (74 samples and 33 blanks) were generated for the entire 2002-2007 SOAP field program from the two rural and four urban/suburban locations described above. Filters were composited to provide sufficient mass for the HPOC analysis by gas chromatography/mass spectrometry (GCMS). Individual molecular markers such as dicarboxylic acids, particularly oxalic (C2), malonic (C3), and succinic (C4), were targeted. Carbonyl compounds also were targeted and included keto mono- and diacids (C2-C5 and C5-C7, respectively) and carbonyls (C2). Overall, these markers totaled 23 individual HPOC. Filter extracts were derivatized with PFBHA (carbonyl specific) and BSTFA (ROH, aryl alcohols and carboxylic acids) and then analyzed by a Shimadzu QP2010 GCMS. The HPOC markers were identified and quantified using authentic standards, characteristic ions and retention times, the NIST Wiley MS Library, and integration software furnished by Shimadzu. The 23 HPOC markers were screened from each SOAP filter composite. Ambient concentrations were determined for the urban NY megacity sites and rural upwind sites. Oxalic acid (C2) was the most dominant marker found, and it was seen at fairly consistent levels across all sites and seasons. We will discuss further results including a comparison of HPOC markers with the analogous PM2.5, EC, OC and TC ambient mass concentrations using scatter plots and regression analysis to determine correlation of a given marker with these larger complex PM2.5 components. Additionally, we will discuss ratios of an HPOC marker with EC, which eliminates mass concentrations and focuses on relative abundances in the megacity region. The SOAP 2002-2007 HPOC results provide molecular level information on the nature of water soluble organic matter in PM2.5 monitored alongside federal air quality programs. This information can be linked to further studies of aerosol chemical properties and effects on physical meteorology in megacity regions.