The literature on lower extremity prostheses from 1989 to 2006 has been reviewed in this article. New technologies, such as the microprocessor-controlled prosthetic knees and energy-storing/return prosthetic feet, are recent advances in the prosthetic field. Despite the extensive research to date in the areas of socket design and manufacturing, and alignment of prostheses for optimum gait analyses, problems persist in the field. Difficulties in obtaining a comfortable socket fit, prostheses weight and alignment guidelines, and the ability to rapidly manufacture a prosthetic socket that can accommodate the changing sizes of the residual limb persist. Furthermore, no prosthetic device can adjust to the typical movements of the human gait. These areas provide opportunities for further research and development.