The objective of the study was to investigate gait symmetry in transfemoral amputees using a hydraulic- and a microprocessor-controlled knee prosthesis. An A-B design with repeated measurements was chosen, and the measurements were carried out at a prosthetics/orthotics rehabilitation center. Nine unilateral transfemoral C-Leg bearing amputees participated in the study, of whom five subjects completed the study. Three-dimensional inverse dynamic gait analysis was performed on each subject. Each subject was then fitted with a 3R60 prosthesis. After a 1-week acclimation period, gait analysis was performed on the 3R60 prosthesis. The outcome measures were temporospatial symmetry, duration of single support on the sound side and the prosthetic side, and the introduced butterfly symmetry ratio. Spatial symmetry was not significantly different between the two prosthetic knees. Temporal symmetry was not significantly improved when subjects used the C-Leg. Single support was significantly longer on the sound side than on the prosthetic side (p < 0.05). However, no significant difference was observed between the two prosthetic knees. The butterfly symmetry ratio was not significantly improved when subjects used C-Leg. The butterfly patterns differed remarkably across subjects, which indicates different gait strategies, but the gait patterns within subjects were not influenced by the type of prosthetic knee. In conclusion, none of the outcome measures investigated showed a significantly improved gait symmetry when subjects used C-Leg compared with the mechanical prosthetic knee 3R60.