A multiyear research project was conducted to investigate the potential of using municipal solid waste combustion bottom ash as a paving material. Characterization of the ash physical properties, development of the asphalt mix designs, and the bottom ash demonstration project in Laconia, New Hampshire, are discussed here. Laboratory results suggest that the physical properties of the ash are consistent with its use as a substitute for conventional aggregate in asphalt mixtures, the properties of ash are typical of a lightweight aggregate, and the 50 percent ash-asphalt mixture design meets New Hampshire Department of Transportation specifications. An ash demonstration project at 50 percent substitution was successfully placed in Laconia in May 1993. A 5-year period of field performance evaluation indicates that the ash section performs as well as the control section.