The papers in this volume, written by authors experienced in intelligibility issues in speech pathology and related fields, describe the basic dimensions by which speech intelligibility can and must be understood. The dimensions are auditory perceptual, linguistic, acoustic and physiologic. These, in turn, are applied to the fundamental problems of definition and theory, measurement and clinical management. Only relatively recently has there been significant progress in formal intelligibility assessment and few, if any books have been published on intelligibility concerns in speech pathology. It is hoped that this book represents the topic of intelligibility in a way that will encourage further invention in research and clinical efforts relating to this essential aspect of speech and language performance.