Methods for the sampling and analysis of diesel particulates have been evaluated. A number of different solvents were utilized for the extraction of diesel particulates. Benzo(a)pyrene (BaP) standards spiked on glass-fiber or quartz-fiber filters were found to be oxidized during the sampling of ambient air or exhaust gases. Such degradation was largely reduced by using filters with more inert surfaces, such as Teflon membranes. The results suggest that sample degradation due to gas-BaP reactions requires the presence of a reactive or catalytic medium, such as the glass-fiber filter surface. Such reactions can be minimized with the proper choice of a more inert filter surface such as Teflon. Oxidation of BaP was also observed in diesel extracts during analytical procedures or prolonged storage for several weeks in the dark. The implication of the sampling and analytical artifact problem is a question not only of analytical recovery but also of whether significant biologically active conversion products are produced. Analytical methods to study the extraction efficiency for BaP from diesel particulates are presented. High-performance liquid chromatography (HPLC), high-resolution mass spectrometry (HRMS), and gas chromatography-mass spectrometry (GC-MS) are being investigated for the identification and analysis of these species and preliminary results indicate the presence of a number of oxygenated polynuclear aromatic hydrocarbon (PAH) compounds, which potentially could be produced by oxidation during sampling and analysis.