We participated in the interlaboratory studies conducted by the National Bureau of Standards/Department of Energy (NBS/DOE) Analytical Characterization Group in which shale oil and diesel particulates were analyzed for three ring to six ring polynuclear aromatic hydrocarbons (PAH). Diesel particulates were extracted by Soxhlet or ultrasonic extraction. The PAH fraction was isolated with Sephadex LH-20 gel filtration chromatography and silica gel adsorption chromatography. The individual PAH was identified and quantitated with a gas chromatography/flame ionization detector and computerized gas chromatography/mass spectrometry. The combination of gel filtration and adsorption chromatography was found to be effective in isolating PAH from various complex sample matrices for further instrumental analysis. The results compared favorably with methods used among the other participating laboratories.