It has been suggested that biomechanical factors play a role in explaining interindividual differences in movement economy, but it is not apparent how important this role is nor how consistently these factors explain such differences. The purpose of this review is to summarize our current state of knowledge regarding the relationships between gait economy and selected body structure and biomechanical factors. Because the research literature contains other review papers on this general topic, it is not the intent to provide a comprehensive analysis of all anatomical and biomechanical factors that have been examined previously. The review considers not only some topics of very recent interest (e.g., Does flexibility/joint range of motion affect gait economy? Can gait mechanics and economy be altered effectively via biomechanical feedback?), but also topics that have been examined considerably over many years (e.g., Is economy of motion associated with body mass, mass distribution, speed of movement, stride length and rate, and gait kinetics?). Results from the many studies reviewed confirm the notion that several structural and biomechanical factors offer some potential for explaining economy differences between individuals. Nevertheless, the relationships that have been observed between economy and individual descriptors of body structural and gait mechanics have generally been weak and inconsistent from study to study. Variables that describe muscular effort appear to have the greatest potential for explaining metabolic energy demands during walking and running. Unfortunately, at present it is unclear what quantifiable descriptors can best reflect muscle force production.