Sway has been measured by Wright's Ataxiameter in 151 frail elderly and five young subjects, and compared with various sensory modalities. There is a close relationship between increased sway and impaired vibration sense in the legs. No correlations emerged with proprioception but this may reflect the imprecision of the test. That neither vision nor vestibular deprivation correlated with sway confirms the place of these senses as secondary in the maintenance of posture. Vestibular impairment was found in only 6% of the elderly subjects, by tilt test--and these were the very old. There was a limited relationship between falls in the past year and both sway and proprioception.