Two patients with "pure akinesia" who showed the characteristic changes of progressive supranuclear palsy (PSP) at necropsy are described. They had akinesia but no rigidity or tremor, and ophthalmoplegia was not observed during the course of illness. The symptoms of "pure akinesia" was not improved by levodopa therapy but was considerably improved by L-threo-3,4-dihydroxy-phenylserine. At necropsy, pathological findings were not different from those reported for PSP. It is suggested that "pure akinesia" is an atypical manifestation of PSP, and that norepinephrinergic neurons may be involved in some types of PSP.