In December 2000, the U.S. Environmental Protection Agency (EPA or the Agency) finalized a comprehensive national emissions control program, the 2007 Highway Diesel (HD 2007) program, that regulates highway heavy-duty vehicles and diesel fuel as a single system. Under the HD 2007 program, the Agency established new emission standards that will significantly reduce particulate matter (PM) and oxides of nitrogen (NOx). The monetized benefits of this program exceed its costs by a factor of nearly 17 to one. Since December 2000, we have conducted a comprehensive progress review of the technologies needed to implement the program. This report documents the findings of our review. Specifically, this report provides our review of the progress of (1) manufacturers of diesel engines and emission control systems in developing technology to reduce engine exhaust pollutants, and (2) the petroleum refining industry in developing and demonstrating technologies to effectively lower the sulfur level of diesel fuel. Consistent with our stated intention in the HD 2007 rulemaking, we are planning to continue monitoring, on an annual basis, industry's progress in introducing technologies to meet the HD 2007 emission standards.