Falls are a major problem for older people, but the underlying mechanisms are not well understood. When a balance disturbance is sensed by the vestibular system, a counteractive whole-body motor response is generated. This demonstrates that this system is a key sensory input for maintaining upright posture. Since age-related changes to the peripheral and central vestibular system have been reported (1, 2), the higher incidence of falls in older people may be partially attributable to a vestibular mechanism. We examined balance reflexes evoked by stochastic vestibular stimulation (SVS) in three groups of human subjects; young (n=9, 28±7years), middle-aged (n=9, 55±6years) and older adults (n=14, 77±4years) (mean±SD). A randomly varying current (filtered white noise, 0-20Hz; RMS amplitude, 0.6mA) was passed between the mastoids of subjects stood with feet together and eyes closed. Medio-lateral ground reaction shear force (Fx) was measured for the duration of each trial (6 x 30sec). The relationship between the stimulating waveform and the evoked motor response was then calculated using the cumulant density function (3). As shown in Figure 1A, the resulting SVS-Fx relationship clearly shows that SVS precedes an initial negative peak (average magnitude=0.05±0.02) followed by a larger positive peak in Fx (average magnitude=0.17±0.05). These two components are termed the short latency (SL) and medium latency (ML) responses, respectively. We found the magnitude of these components to be differentially affected by ageing (mixed design ANOVA, age group x component; F2,29=10.4, p<0.001, n=32). As shown in Figure 1B, the SL response tended to decrease in older adults, though this effect was not significant. In contrast, the ML response was substantially and significantly increased in middle-aged and older adults (pairwise comparisons, both p<0.04). Although the origin of the SL motor response is unclear (4), the ML response has been attributed to a virtual semicircular canal signal of head roll, and its direction is congruent with the resulting body sway. Our results therefore demonstrate that the functional balance response evoked by electrical activation of semicircular canal afferents is increased in older people. Since the site of electrical activation bypasses the end organ mechanics, this finding may reflect an increased afferent or central sensitivity in order to compensate for an age-related loss of peripheral vestibular hair cells (1).