A six chamber system for exposing rodents to oil shale and diesel aerosols was designed and constructed. Four-inch fluid bed generators were used for generating oil shale aerosols and two 5.7 liter diesel engines were used for generating diesel exhaust. An aerosol delivery/dilution system was designed to provide control of aerosol concentrations. Filter samples and cascade impactors ere used to characterize exposure aerosols. During the first five months concentrations in the exposure chambers were from 2 to 9% of target concentrations.