Progressive supranuclear palsy (PSP) is characterized by symptoms of disturbance of eye movement, nuchal rigidity, parkinsonism and subcortical dementia. Its pathology reveals that Alzheimer's neurofibrillary tangles (NFTs) are situated especially in the nuclei of basal ganglia and brainstem. It has been pointed out that NFTs observed in PSP are composed of straight tubules, the width of which is about 15 nm. This report is to reappraise the ultrastructure of NFTs observed in three cases of PSP. They are case 1; 69-year-old male, case 2; 62-year-old female and case 3; 65-year-old male. The clinical features of three cases were characterized by above-mentioned symptoms. Many NFTs were observed in brainstem of case 1 and 3. NFTs seen in brainstem of case 2 were in a small amount. In case 1 and 2, there were many NFTs in cerebral cortex, especially in parahippocampal gyri and other limbic areas. We examined the portions of frontal cerebral cortex, parahippocampal cortex, the basal nucleus of Meynert, oculomotor nucleus, substantia nigra, pontine nuclei and locus caeruleus of case 1, substantia nigra, red nucleus and inferior olivary nucleus of case 2, and Ammon's horn, globus pallidum, subthalamic nucleus, substantia nigra, oculomotor nucleus, pontine nuclei, locus ceruleus and inferior olivary nucleus of case 3. Ultrastructurally, NFTs of frontal cortex of case 1 consisted of twisted tubules and those of hippocampal and parahippocampal cortices of case 1 consisted of straight and twisted tubules, being observed separately in neurons. The NFTs of brainstem of case 1 and 2 were mainly composed of 12-17 nm straight tubules, and twisted tubules occasionally intermingled with straight components. In locus ceruleus of case 1, a single straight tubule could be seen in the bundles of twisted tubules. NFTs of case 3 were composed of only straight tubules, the width of which was about 15 nm. Twisted components were not observed in neurons of each nuclei of case 3. The characteristic ultrastructure of NFTs in PSP has been an appearance of straight tubules, however, twisted tubules were occasionally observed in this study. There are several case reports which demonstrated an appearance of both straight and twisted components. It is easily presumed that the process of aging takes part in the accumulation of twisted fibrils. However, it is now under consideration why twisted tubules are also observed in PSP. To summarize this study, the cases with many NFTs observed in widespread cerebral cortex may have a tendency to show both straight and twisted tubules.