Abstract Military personnel are exposed to intense noise during their active duty careers from weaponry, explosions and military vehicles such as tanks, helicopters and other aircraft. Exposure to intense noise causes hearing loss and may also cause vestibular dysfunction. Although hearing loss and cochlear synaptopathy are well studied, peripheral vestibular synaptopathy and vestibular dysfunction are less often studied and poorly characterized. Furthermore, age related balance deficits are a significant public health problem for veterans in the United States. Agrawal et al. reported that 35% of adults older than 40 had evidence of postural instability and balance dysfunction increased with age so that by 80 years, 85% of adults reported balance problems. Vestibular dysfunction can increase the likelihood of falling; in the US falls are responsible for significant decrements in quality of life, and more than 50% of accidental deaths. Although the causes of postural instability are complex and multifactorial, several studies demonstrate a linkage between noise induced hearing loss and vestibular dysfunction in humans. Noise exposure as a risk factor for vestibular loss has obvious and significant veteran health implications, but there are few, if any studies that (1) provide insights into the physiology that underlies noise-induced vestibular loss and (2) provide guidance for preventative or rehabilitative strategies for veterans with balance disorders. The proposed studies will show in a rat model, that noise exposure at levels encountered by veterans during their military service and during daily life can cause vestibular dysfunction that includes deficits in vestibular reflexes and vestibular signaling that increase fall risk and reduce head stability and visual acuity during movement. We hypothesize that intense noise exposure sufficient to attenuate vestibular nerve responses to linear acceleration (as assessed by the Vestibular short latency Evoked Potential (VsEP) will also cause significant functional deficits in three vestibular dependent behaviors, (1) control of balance during locomotion; (2) deficits in vestibulocollic reflex function that reduce head stability; and (3) deficits in vestibulo-ocular reflex function sufficient to reduce visual acuity during locomotion. Specific Aim 1. Assess balance, head, and visual stability in rats exposed to intense noise sufficient to abolish VsEP responses for at least 28 days. We will use this time window to probe the time course and nature of deficits in vestibular dependent behaviors caused by noise exposure. Specific Aim 2A. Determine whether or not the same behaviors are impaired by a single noise exposure that induces temporary loss and recovery of VsEP responses within 28 days. This Aim will determine if there is a functional vestibular impact from a single noise exposure after which peripheral synapses and VsEP responses recover. Specific Aim 2B. Determine the extent to which and the time ...