The results of an analysis of heavy-duty truck (Classes 2b through 8) technologies conducted to support the Energy Information Administration's long-term projections for energy use are summarized. Several technology options that have the potential to improve the fuel economy and emissions characteristics of heavy-duty trucks are included in the analysis. The technologies are grouped as those that enhance fuel economy and those that improve emissions. Each technology's potential impact on the fuel economy of heavy-duty trucks is estimated. A rough cost projection is also presented. The extent of technology penetration is estimated on the basis of truck data analyses and technical judgment.