This study represents the first comprehensive treatment of the sound system of the Hittite language and its historical development in a quarter-century. It is the very first attempt at a systematic description of the sound systems of all the ancient Indo-European languages of Anatolia. It codifies the results of a generation of collective scholarship which has made some dramatic advances, offers a number of new hypotheses, and frames the problems which remain to be solved. The contents will be of interest to Indo-Europeanists for the new perspectives on the crucial Anatolian subgroup and to scholars of second-millennium Anatolia for the up-to-date descriptions of the extant Indo-European languages of that era.