We reported a case of myelopathy of unknown etiology with transient spinal automatism. A 50-years old woman suffered from gait disturbance with weakness and abnormal involuntary movement of both lower limbs. The involuntary movement showed like as triple flexion reflex and appeared in the interval between some seconds and some ten seconds. It was consisted of non-reciprocal phasic-tonic discharges. In electrophysiological examination, long latency muscular responses were observed following F wave and MEP (motor evoked potential) in the abductor hallucis muscle. Excitability of motoneurons of lower limb muscles following stimulation of sural nerve was evaluated by means of H reflex and averaged surface EMGs. Short latency facilitation was induced in the soleus and tibialis anterior muscles contrary to inhibition in the control subjects. In this case, reduced activity of inhibitory and/or enhanced activity of excitatory interneurons to motoneurons attributed to the pathophysiology of spinal automatism.