We evaluated the ability of seven devices to immobilize a prosthetic ankle-foot complex against plantarflexion, dorsiflexion, inversion, and eversion forces: two casts (plaster of Paris and Fiberglas) and five removable braces (molded ankle/foot orthosis, composite boot brace, pneumatic boot walker, nonarticulating fracture boot, and ankle stirrup). Each device was applied to a prosthetic ankle-foot complex and evaluated on a test frame for resistance to sagittal motion and coronal torque. Results showed that casts offered significantly (P < or = 0.05) more resistance to motion in all directions tested than did the braces. The resistance offered by the devices tested depends on the conformity of the device to the shape of the foot in that plane and the material properties of the device. Braces offer the advantage of being easily removed and reapplied. Different braces offer specific advantages and disadvantages in different planes tested, and immobilization selection should be individualized based on this information.