A mix of anthropogenic and biogenic emissions, coupled with hot and humid summer climatology, leads to high ozone (O3) and fine particulate matter (PM2.5) formation in the southeastern U.S. where extensive air quality field and modeling studies have been performed in the past years. Understanding governing processes and reactions for major air pollutants is a key to the development of effective control strategies for future attainment of O3 and PM2.5. In this study, the process analysis (PA) tool embedded in the U.S. EPA Models-3/Community Multiscale Air Quality (CMAQ) modeling system is applied to gain more in-depth understanding of atmospheric processes and chemical reactions. PA consists of Integrated Process Rates (IPR) and Integrated Reaction Rates (IRR) analysis. IPR quantifies the contributions of atmospheric processes to gaseous and PM species concentrations; IRR quantifies reaction rates of gaseous species. Simulations with CMAQ-PA are being conducted for four representative months in 2002 (i.e., Jan., Apr., Jul., and Oct.) at a 4-km grid resolution over a southeastern domain that covers North Carolina, South Carolina, and portions of Georgia. PA is used to identify controlling processes and dominant reactions for major air pollutants in each season to provide guidance for emission control strategies. In addition, simulations under future-year (i.e., 2018) emission scenarios will also be conducted to study the impact of controlled emissions on future-year air quality. This study has important implications to a mechanistic understanding of the formation and fate of O3 and PM2.5 and their mitigation through state implementation plans in this region.