PM2.5 samples were collected from June 2005 to December 2005 in Potsdam, NY and analyzed for polar organic compounds by GC/MS. The major compounds that identified in the samples included 2-methyltetrols (2-methylthreitol and 2-methylerythritol), levoglucosan, iso-pinonic acid and mannitol. 2-methyltetrols were quantified during the analysis. A seasonal variation with the highest concentrations during the summer, and the lowest concentrations during the winter time were observed for these two diastereoisomers. At the same time, OC/EC analysis of these samples was performed. The variation of the carbon contribution of 2-methyltetrols to OC was found to follow the same pattern as the concentration variation of 2-methyltetrols. During the high photochemical oxidation period, the maximum carbon contribution of 2-methyltetrols to OC was 2.8%. According to the observed results with highest concentration of 2-methyltetrols during summer season, it can be concluded that isoprene photochemical oxidation products is a more important source of secondary organic aerosol (SOA) at Potsdam area during summer.