We report a case of a 52-year-old man with posttraumatic parkinsonism. He was admitted to our department because of right-sided hand tremor and gait disturbance. He had suffered from a severe head injury incurred in a traffic accident with brief unconsciousness 6 months before admission. Three weeks after his injury, tremor and rigidity in the right upper limb developed, and he walked dragging his right leg. Five months after his injury, he received 1-dopa therapy, exhibiting a moderate improvement in parkinsonian symptoms. On admission, he was demented to a mild degree with masked face and monotonous speech. He presented with resting-postural-kinetic tremor and muscle rigidity on the right side. Cranial CT and MRI showed no abnormality. Inter-peak latencies of waves III to V of BAEP were significantly longer in this patient than in normal subjects. This BAEP findings suggested an upper brainstem lesion. 123I-IMP SPECT disclosed decreased cerebral blood flow in the left thalamus, bilateral frontal and parietal cortices. We diagnosed this case as having posttraumatic parkinsonism. Parkinsonism in the present case may be due to the involvement of multiple neuronal circuits of the extrapyramidal system at the level of the midbrain to the thalamus.