We constructed a powered ankle-foot orthosis for human walking with a novel myoelectric controller. The orthosis included a carbon fiber and polypropylene shell, a metal hinge joint, and two artificial pneumatic muscles. Soleus electromyography (EMG) activated the artificial plantar flexor and inhibited the artificial dorsiflexor. Tibialis anterior EMG activated the artificial dorsiflexor. We collected kinematic, kinetic, and electromyographic data for a naive healthy subject walking with the orthosis. The current design improves upon a previous prototype by being easier to don and doff and simpler to use. The novel controller allows naive wearers to quickly adapt to the orthosis without artificial muscle co-contraction. The orthosis may be helpful in studying human walking biomechanics and assisting patients during gait rehabilitation after neurological injury.