An evaluation of historic flood estimates in mountainous areas in Colorado was made to assess their accuracy. The purpose of this evaluation is to enhance awareness of the need to assess the accuracy of historic flood peaks, particularly floods of record, because they are such a critical factor in flood-plain management, design of hydraulic structures in flood plains, and related environmental studies. Research needs based on a proposed river-system-process approach are suggested. A critical need exists for interdisciplinary documentation of extreme-flood processes, particularly to improve methods to directly measure extreme floods and quantify total energy losses. Such research will benefit the public through improved engineering designs and environmental investigations.