In Lexical Strata in English, Heinz Giegerich investigates the way in which alternations in the sound patterns of words interact with the morphological processes of the language. Drawing examples from English and German, he uncovers and spells out in detail the principles of 'lexical morphology and phonology', a theory that has in recent years become increasingly influential in linguistics. Giegerich queries many of the assumptions made in that theory, overturning some and putting others on a principled footing. What emerges is a formally coherent and highly constrained theory of the lexicon - the theory of 'base-driven' stratification - which predicts the number of lexical strata from the number of base-category distinctions recognized in the morphology of the language. Finally, he offers accounts of some central phenomena in the phonology of English (including vowel 'reduction', [r]-sandhi and syllabification), which both support and are uniquely facilitated by this new theory.