Research concerning structure and processing in the mental lexicon has achieved central prominence within cognitive psychology and psycholinguistics. Historically, however, much of the research on the lexicon focussed not on its role in language comprehension, but as a medium for studying semantic memory. This picture has changed in recent years, with much more research examining the role of lexical processes and output in language comprehension. Gathered together in this volume is the work of some of those researchers who are responsible for this shift of emphasis. Chapters deal with the role of sentence contexts in word recognition, processes involved in the activation and enhancement of lexical information, and the interaction of lexical and syntactic information in sentence processing. A wide range of theoretical and empirical issues relating to language understanding are discussed.