The surface sensitivity and minimal fragmentation available with time-of-flight secondary ion mass spectroscopy (TOF-SIMS) makes it a powerful tool for the examination of the organic and inorganic species on individual particle surfaces. One concern with the technique is the potential loss of volatile and semi-volatile organic compounds in the high vacuum environment. Cryo-cooling in the intro chamber enables us to retain semi-volatile compounds including PAHs and alkanes on surfaces for over an hour in the analytical chamber. Samples collected using an eight-stage Graseby-Anderson cascade impactor included aerosols from winter snowmobile emissions in Yellowstone National Park and urban aerosol from the Salt Lake Valley. Comparison of spectra obtained at ambient temperature with those obtained under cryogenic conditions show a clear loss of both aromatic and aliphatic organic species at ambient temperature. (C) 2003 Elsevier B.V. All rights reserved.