An autopsy case of stiff-man syndrome is presented. The patient was a 54-year-old man who had suffered from fluctuating rigidity and tonic spasm of the trunk and leg muscles for three years. These symptoms were induced by emotional stress, strain at voiding and other external stimuli. Physical examination revealed stiffness of the neck, trunk and legs without obvious muscle weakness or atrophy. Deep tendon reflexes were hyperactive, while sensation was normal. EMG showed the stiffened muscles to have continuous motor unit activity which was decreased by myoneural block, spinal anesthesia, diazepam or sleep. Administration of diazepam (60 mg daily) gave some relief of the stiffness for several days. However, respiratory arrest suddenly occurred. Although the patient was resuscitated, he died nine days after this episode. Examination of the spinal cord revealed loss and degeneration of nerve cells with marked gliosis in the medial motor nuclei of the anterior horns. A symmetric degeneration in the bilateral anterior columns which has never been described as a spinal cord lesion in the stiff-man syndrome was also seen.