A facility has been assembled that provides a controlled inhalation exposure to freshly diluted and mixed diesel exhaust using a diesel engine under load and a two-stage exhaust dilution system with dynamic feedback control. The concentrations of particulate matter less than 2.5 microm in diameter (PM(2.5)), particulate carbon, and gaseous pollutants including carbon monoxide and oxides of nitrogen (NOx) have been characterized and the exposure conditions have been found to be both stable and reproducible. Control of the PM(2.5) concentration at intended levels relies on the relatively linear relationship between particle light scattering and exhaust particle mass concentration. While the exposure system does not entirely replicate diesel exhaust conditions in the atmosphere due to the relatively low ratio of nitrogen dioxide to total NOx, the fine particulate matter size distributions are quite similar to those of aged diesel exhaust. The facility enables study of the relationship between diesel exhaust and cardiovascular and respiratory health effects in human and animal models.