This is a 5-site randomized clinical trial of a task-oriented locomotor intervention for acute spinal cord injury (SCI). The intervention, body weight-supported treadmill training (BWSTT), partially supports the weight of the patient via an overhead lift attached to a harness. Therapists train the patient to walk on a treadmill by correcting gait deviations and manipulating sensory input that enhance control of the stance and swing phases of walking at increasingly higher speeds and less weight support. 100 patients with incomplete SCI (from below C4 to T10/11) and 100 patients with lesions at T12 to L3 will be randomly assigned to 12 weeks of conventional therapy programs for mobility versus the same intensity and duration of a combination of conventional therapy plus BWSTT. The primary outcome measures are the level of independence for ambulation and the maximal speed for walking 50 feet. Patients will be tested by masked examiners before and after the 12 weeks of therapy, and 6 and 12 months after entry into the study.