The current conflicts in Afghanistan (Operation Enduring Freedom; OEF) and Iraq (Operation Iraqi Freedom; OIF) have resulted in unprecedented rates of exposure to high-intensity blasts and resulting brain injury. Dennis (2009) reports that during 2005-2007, 68% of U.S. military personnel injured in the OEF/OIF conflicts had blast-related injuries and 28%-31% of those evacuated to Walter Reed Army Medical Center (WRAMC), Washington, DC had brain injuries. While the common focus of auditory evaluation is on damage to the peripheral auditory system, the prevalence of brain injury among those exposed to high-intensity blasts suggests that damage to the central auditory system is an equally important concern for the blast-exposed Veteran. Discussions with clinical audiologists and OEF/OIF Veterans Service Office personnel suggest that a common complaint voiced by blast-exposed Veterans is an inability to understand speech in noisy environments, even when peripheral hearing is within normal or near-normal limits (see attached letters of support). Such complaints are consistent with damage to neural networks responsible for higher-order auditory processing. This proposal is the second phase of a research project focused on examining the degree to which central auditory processing (CAP) dysfunction is a result of blast exposure. Over the initial period of funding, data collection at WRAMC and the VA RR&D National Center for Rehabilitative Auditory Research (NCRAR) established that CAP dysfunction is present in Warfighters exposed to high-intensity blasts while serving in combat. Recently blast-exposed patients with and without diagnoses of mild traumatic brain injury (mTBI) tested at WRAMC showed differences from controls tested at NCRAR on one or more behavioral and neurophysiological tests used to evaluate central auditory function. This project will 1) develop a more accurate estimate of the prevalence of central auditory dysfunction among Veterans exposed to blasts over the past ten years, 2) identify the functional outcomes associated with abnormal performance on tests of central processing, and 3) improve understanding of the ways in which blast-exposure resembles and differs from both the normal aging process and non-blast-related TBI in terms of performance on tests of central auditory processing.