In this study, the influence of different prosthetic alignments and components on oxygen consumption and the important biomechanical characteristics of the normal gait pattern of leg amputees was investigated. With 15 transtibial and 12 transfemoral amputees, the oxygen consumption during walking on a treadmill was analyzed and biomechanical parameters during walking on even ground at a self-selected speed were defined. The amputation of all patients was caused by trauma. Variations of the prosthetic alignment affect the energy consumption of transfemoral amputees more significantly than that of transtibial amputees. Comparison of different prosthetic feet worn by transtibial amputees did not show significant differences regarding metabolic parameters. Compared with conventional hydraulic knee controls, the oxygen consumption of transfemoral amputees provided with an electronically controlled hydraulic knee joint is reduced. All investigated variations can be clearly characterized by the sagittal moments acting on the joints of the prosthetic limb during gait.