Topics in Phonological Theory is a six-chapter text that provides an explication of some of the most important problems in phonological theory, with a few, necessarily tentative, solutions. The first chapter deals with the problem of abstractness in terms of a series of successively weaker constraints that might be placed on the relationship between the underlying and phonetic representations of a morpheme. The second chapter begins with a discussion of the various ways in which the phonetic basis of a rule may be lost in the course of historical change, which lays the groundwork for a lengthy survey of the types of grammatical and lexical conditions that may control the application of a phonological rule. The third chapter describes the constraints and conditions on phonological representations, particularly the domain of these constraints, the level at which they hold, and their duplication of phonological rules. The fourth chapter examines the problem of natural rule interactions, focusing on Kiparsky’s theories of maximal utilization and opacity-transparency and their deficiencies. The fifth chapter deals with Chomsky and Halle’s simultaneous application principle as well as with more recent proposals The sixth chapter compares the relative merits of global rules versus rule ordering for the description of opaque rule interactions.