We compared the vesicourethral function between progressive supranuclear palsy (7 cases) and Parkinson's disease (vesicourethral function study in 8 patients with dysuria and questionnaire study in 44 patients). The frequency of urinary incontinence in the 44 patients with Parkinson's disease was 38.7%. Vesicourethral function study showed hypersensitivity, low bladder capacity, detrusor hyperreflexia and normal sphincter EMG. The frequency of urinary incontinence in supranuclear palsy was 85.7%. Vesicourethral function study showed hyposensitivity and detrusor hyperreflexia in 6 cases, and 4 of these 6 cases had residual urine due to impaired detrusor contraction in micturition phase and/or abnormal sphincter EMG. Compliance was normal, but bladder capacity was decreased in progressive cases. Impaired contraction and hyposensitivity made it more difficult to control the urinary incontinence in supranuclear palsy than in Parkinson's disease. Dementia and lower ADL were frequently accompanied with supranuclear palsy (rare in Parkinson's disease). These were other factors that worsen the control of incontinence.