This study evaluated the effect of levels of hardness of a commonly used orthosis material in reducing plantar pressure in patients at high-risk for foot ulcers. The mean peak pressure was measured, by using the Pedar System, on 19 patients with diabetes mellitus and a history of plantar foot ulceration. Patients walked in standard extra-depth shoes with no orthoses, standard extradepth shoes with 1/4-inch Poron® orthoses in seven different levels of hardness (14, 17, 22, 27, 32, 40, and 55 Shore “O” durometer), and their own nonstandardized footwear with molded orthoses. Mean peak walking pressures were lower in the standard shoes with the 22, 27, and 32 durometer Poron orthoses compared with those in the standard shoes with the 14, 17, and 55 durometer Poron orthoses. Walking pressures were lowest in the patients' nonstandardized footwear fitted with molded orthoses. Results support the use of medium-hardness Poron materials, which includes the current standard formulation (22 Shore “O” durometer), in orthosis fabrication in patients with diabetes at high risk for foot ulceration.