The Coordinating Research Council and the Air Pollution Control Office of the Environmental Protection Agency have jointly supported the Air Pollution Research Advisory Committee Project CAPE-7-68 to analyze and identify the odor-relevant compounds present in diesel exhaust gases. This paper summarizes the experimental results obtained by Illinois Institute of Technology Research Institute and Arthur D. Little, Inc. Both contractors found certain fuel fractions to be odor relevant. Many mono and polyoxygenated partial oxidation products have been identified, at least by structural class. These odorous compounds occur at very low concentrations in the exhaust gases.