The focus of this research is age-related hearing loss (presbyacusis). Currently, nearly 28 million Americans have impaired hearing, and approximately 75% of these persons are over the age of 55. The prevalence of presbyacusis will increase substantially by the year 2020. To meet the challenges of this most prevalent handicapping condition, new information, diagnostic methods, rehabilitation procedures, and cost-effective access to new technologies will be of great importance. Prevention of presbyacusis and/or a reduction in its prevalence are even greater challenges. The overall objective of our research program is to improve diagnostic, rehabilitative, and preventive measures. Towards this objective, three research projects are proposed. by Mills is a study of individual differences in psychophysical and electrophysiological properties of the aging auditory systems of human subjects. Project by Dubno addresses basic questions related to the understanding of speech in realistic listening environments by younger and older human subjects with normal and impaired hearing. Project by Shulfe focuses on morphologic and molecular changes in the aging human cochlea. In addition, two cores provides administrative, technical, and scientific support including the recruitment of human subjects. The proposed program of research on presbyacusis in the long term will influence health care of the presbyacusis patient, will affect care of hearing- impaired persons in general, and will have significant impact on theoretical and applied issues in the science of audition.