Study Design Single cohort study. Objectives To investigate the efficacy of real-time biofeedback provided during treadmill gait training to correct knee hyperextension in asymptomatic females while walking. Background Knee hyperextension is associated with increased stress to the posterior capsule of the knee joint, anterior cruciate ligament, and the anterior compartment of the tibiofemoral joint. Previous methods aimed at correcting knee hyperextension have shown limited success. Methods Ten women, ages 18 to 39 years, with asymptomatic knee hyperextension during ambulation, were provided with 6 sessions of real-time feedback of kinematic data (Visual 3D) during treadmill training. Gait evaluations were performed pretraining, posttraining, and 1 month after the last training session. Results Participants showed improved control of knee hyperextension during overground walking at 1.3 m/s at posttraining and at 1 month posttraining. Conclusion The present study demonstrated that knee sagittal plane kinematics may be influenced by gait retraining using real-time biofeedback. J Orthop Sports Phys Ther 2011;41(12):948–952, Epub 25 October 2011. doi:10.2519/jospt.2011.3660