A major goal of hearing research is to explain how the human auditory system normally functions and to help identify the causes of and treatments for hearing impairment. Experimental approaches to this research make use of animal models that are developed, evaluated and validated to determine what can be generalized from one species to another. By investigating the structures, physiological functions and hearing capabilities of various species, comparative hearing research establishes the biological and evolutionary context for such models. This volume brings together our current understanding of the auditory systems of two of the major vertebrate classes, fish and amphibians. It overcomes the differing theoretical and experimental paradigms that underlie most work on these groups and treats both fish and amphibians together in most chapters in order to address broader comparative issues.