A 48-year-old man, who had spastic tetraplegia and a marked atrophy of the medulla oblongata and upper cervical cord, was reported. He began to walk in spastic fashion at the age of 12 years, and was diagnosed as spastic paraplegia. His father, whose onset of the disorder was 35 years old and died of pneumonia at the age of 69 years, manifested symptoms and a course, both resembling those of the present patient. Generalized weakness progressed gradually, and the patient was confined to bed in his forties. On admission, he showed markedly increased tendon reflexes and pathological reflexes in all the extremities. Muscular weakness was severe in the neck, trunk and extremities, and mild in the facial muscles. There were neither bulbar sign, significant respiratory failure nor fasciculation of muscles. A needle EMG examination revealed no apparent neuropathic findings. MR imaging showed a marked atrophy of the medulla oblongata and upper cervical cord, which was not considered to be secondary to vascular or infectious diseases. Though sensory evoked potentials showed no response at the latencies of central nervous components, visual evoked potentials, brainstem auditory evoked response and blink reflex were normal. This case might represent an unknown hereditary degenerative disease with autosomal dominant inheritance.