At least six brands of energy-storing prosthetic feet (ESPF) are now commercially available in the US. These are designed to permit lower extremity amputees to participate in a wide variety of activities, such as running and jumping sports, as well as vigorous walking. Although kinesiologic studies of these devices have not been completed, clinical experience suggests that the Flex-Foot provides the highest performance, followed by the Carbon Copy II and the Seattle Foot. The S.A.F.E. Foot, the STEN Foot, and the Dynamic Foot provide less energy storage and may be suitable for less active patients or those with special needs such as walking on uneven ground. All of the ESPF except the Flex-Foot may be attached to a realigned conventional prosthesis. The Flex-Foot incorporates a pylon and foot in one unit and requires special fabrication technologies. The additional cost of most of the ESPF (compared to a Solid Ankle Cushion Heel Foot) may add little to the cost of a finished prosthesis although it provides greatly increased function. The Flex-Foot, however, is significantly more expensive. Advances in kinesiology and materials science are being applied in the design of prosthetic components that are lighter, stronger, and more resilient. Clinicians can now choose from a variety of innovative commercially available devices but have been hampered by a lack of published information. This paper will review the design philosophy, materials, and applications of ESPF, and will supplement the information available from individual manufacturers and the prosthetic literature.