Ankle-foot orthosis (AFO) is known to correct abnormal gait patterns and improve walking stability and speed in patients with hemiparesis. To quantify these benefits in post-stroke gait, a three-dimensional motion analysis of gait pattern was conducted. Forty patients with hemiparesis were enrolled. A three-dimensional motion analysis system was used to analyze patients’ treadmill walking with/without an AFO. Outcome measures were 12 abnormal gait indices (forefoot contact, knee extensor thrust, retropulsion of the hip, flexed-knee gait, medial whip in the stance phase, circumduction gait, hip hiking, insufficient knee flexion during the swing phase, excessive lateral shifting of the trunk, contralateral vaulting, excessive hip external rotation, and posterior pelvic tilt), calculated using kinematic data and spatiotemporal indices, and the symmetry index of double-stance and single-stance time and step length. Forefoot contact (without AFO vs. with AFO: 71.0 vs. 65.8, P