Extraordinary progress has been made in recent years in understanding the cellular and molecular basis of development. This progress is having a strong influence on our knowledge of the auditory system. From the molecular genetics of ear development to the ontogeny of auditory capability, great inroads have been made. The contributors to this volume on development of the auditory system have provided a detailed and integrated introduction to the behavioral, anatomical, and physiological changes that occur in the auditory system of developing animals.