The effect of emission control devices on the particulate emissions of an automotive power plant was investigated. The work was divided into five tasks as follows: TASK I was the characterization of a particulate trapping system, and the determination of what effects, if any, were noted as conditions within the system were controllably varied; TASK II was the definition of a particulate baseline for a 1972 400 CID engine, using non-leaded and low lead fuel--no emission control devices were used for the baseline runs; TASK III was the evaluation of the particulate emission from a 1972 400 CID engine equipped with the following control devices--three different oxidation catalysts one NOx catalyst, and one exhaust gas recirculation system; TASK IV involved testing automobiles equipped with control devices for particulate emissions--these vehicles were supplied by both the contractor and the Government; and TASK V was to define a preliminary collection system for diesel engine particulate sampling. In all tasks, particulate mass emission rates were measured, as well as particle mass size distribution, carbon and hydrogen, tract metal, and benzo-a-pyrene content of the particulate. Ammonia and aldehydes were measured in the exhaust gas condensate, and gaseous emissions were determined as a routine check on engine operating conditions. (Modified author abstract)