ABSTRACT: This article elucidates the effect of prosthetic foot on the residuum-socket interface (RSI) pressure and gait characteristics in a man with transtibial osteomyoplastic amputation (TOA). The study evaluates the effect of three prosthetic feet, including 1) Renegade Foot® from Freedom Innovations (Irvine, CA), 2) Venture Foot™ from College Park (Fraser, MI), and 3) Proprio Foot® from Össur (Reykjavik, Iceland) in six gait activities: walking forward at “normal” pace, walking forward at fast pace, ascending and descending a staircase, and ascending and descending a ramp. Force resistive sensors were placed at six locations, including distal anterior end-bearing, middle posterior, and four proximal points inside the prosthetic socket, to capture real-time RSI pressures. Whereas nominal values of pressure were observed in the proximal region, greater pressure was observed at the distal anterior end-bearing region of the socket, which confirmed one of the intended outcomes of the TOA procedure. Of 36 statistical tests (t-test, p < 0.05), 35 tests (97.2%) confirmed the hypothesis that when the same prosthetic foot was used in the same gait activity, peak and mean pressures are greater at the distal anterior end-bearing location than at other locations. Furthermore, 182 of 216 (84.2%) statistical tests (t-test, significance level of 0.05) supported the hypothesis that at the same measured location during the same gait activity, different prosthetic feet result in different peak (or mean) RSI pressures. Coefficients of variation of the mean sustained pressures showed that when the gait activity was changed, each prosthetic foot affected the sustained pressure differently, even at the same measured location. Each prosthetic foot also had a direct effect on temporal gait parameters such as stance phase and gait cycle durations. These results elucidate the importance for clinicians to understand the characteristics of different prosthetic foot designs to match with the specific needs of the client with amputation.