• Must be over 35 years of age and present with gradual progression of PSP-related symtoms

• Must have an informant or study partner that can provide independent information of functioning.

• Must meet criteria for possible or probable Progressive Supranuclear Palsy. To fulfill criteria for possible PSP, subjects must have a gradually progressive disorder with either vertical (upward or downward) supranuclear palsy or both slowing of vertical saccades and prominent postural instability with falls in the first year of disease onset. To fulfill criteria for probable PSP, subjects must have vertical (upward or downward gaze) supranuclear palsy and prominent postural instability with falls in the first year of disease onset.