Progressive supranuclear palsy is a neurodegenerative disease which affects the brainstem and basal ganglia. Patients present with disturbance of balance, a disorder of downward gaze and L-DOPA-unresponsive parkinsonism and usually develop progressive dysphagia and dysarthria leading to death from the complications of immobility and aspiration. Treatment remains largely supportive but, potentially, treatments based on cholinergic therapy may be useful. As in Alzheimer's disease, the neuronal degeneration is associated with the deposition of hyperphosphorylated tau protein as neurofibrillary tangles but there are important distinctions between the two diseases. Evidence from familial fronto-temporal dementia with parkinsonism linked to chromosome 17 suggests that tau protein deposition is a primary pathogenic event in some neurodegenerative diseases. The understanding of the mechanism of tau deposition in progressive supranuclear palsy is likely to be of importance in unravelling its aetiology.