This report reviews new vehicle fuels and technologies that are likely to be commercially available within the next 10 years in the United States and other industrialized countries at a level that could result in significant population exposure. It highlights expected changes in emissions and other effects from the use of each technology and fuel, along with any life-cycle and regulatory issues. This Communication was prepared by the Special Committee on Emerging Technologies (SCET) whose 18 members include government, academic, industrial, and other experts from diverse fields, including automotive engineering and emissions, emissions control technologies, new fuels, electric vehicles, and environmental modeling. The report identifies many high-priority areas for research. In response, the HEI Research Committee has developed an Action Plan that describes the steps the Committee is taking, or plans to take, to address the high-priority issues identified by SCET.