Poor air quality along the U.S.-Mexico border is of serious concern due to its impact on public health. Pollutants such as particulate matter, nitrogen oxides, and ozone (for which nitrogen oxides are a precursor) can contribute to respiratory illness and even premature death in exposed populations. Emissions from diesel engines are a significant source of air pollutants in the border region. In order to address the health threats posed by diesel emissions, the Good Neighbor Environmental Board (GNEB), which is a federal U.S.-Mexico border advisory panel, recommended reducing emissions from diesel trucks, buses, municipal and private fleets, and passenger vehicles to address air pollution in the border region. GNEB also suggested that U.S. Environmental Protection Agency (U.S. EPA) work closely with its Mexican counterpart, SEMARNAT, local agencies, and private stakeholders to promote a clean diesel corridor strategy along the border. This report is intended to provide the U.S. EPA with a summary of available information regarding diesel emissions in the border region to inform development of a clean diesel corridor strategy. In particular, this report seeks to provide a detailed discussion of the unique characteristics of transportation and trade in the border area, its linkages with increasingly globalized trade patterns, and how diesel emissions associated with this trade are projected to change in the future. Specific research topics addressed in this analysis include: Current inventories of emissions along the border; Sources of diesel emission in the U.S.-Mexico border region, including commercial transport vehicles (i.e., trucks, trains, and ships) and other mobile sources of diesel emissions (e.g., municipal bus fleets, school busses, and construction equipment); Current transportation corridors along the U.S.-Mexico border; Patterns of goods movement across the border into the interiors of the U. S. and Mexico; Characteristics of truck and rail fleets that move goods throughout the border region; Voluntary and regulatory programs that affect diesel emissions; Projected trends in transportation dynamics and diesel emissions along the Border; Factors that influence diesel emissions, e.g., border crossing delays.