The purpose of the study is to provide a comprehensive assessment of the costs and environmental effects of the control of diesel particulate emissions and to recommend a regulatory strategy for their control. As such, the study expands, updates and combines the regulatory analyses supporting the light-duty diesel particulate final rule and the heavy-duty diesel particulate proposed rule. The study identifies current and future diesel particulate emissions and exposure levels, assess the health and welfare impact of diesel particulate, and estimate the costs of controlling diesel particulate emissions to various levels. The study also integrates these aspects of diesel particulate control and will develop, evaluate, and recommend a regulatory control strategy.