Lexical effects on language processing are currently a major focus of attention in studies of sentence comprehension. This thematic collection provides a uniquely multi-faceted and integrated viewpoint on key aspects of lexicalist theories, drawing from the fields of theoretical linguistics, computational linguistics, and psycholinguistics. The focus of this stimulating volume is on a number of central topics: The discussion of foundational issues concerning the nature of the lexicon and its relationship to sentence understanding; the exploration of the relationship between syntactic and lexical processing; and the investigation of the specific content of lexical entries, especially for verbs. The authors draw on a range of methodologies, from computational modeling to corpus studies to behavioral and neuro-imaging experimental techniques. The breadth of topics and methodologies is brought together by the articulated, critical analysis of the field provided in the introduction. The research reported here elaborates both the structure and the probabilistic content of lexical representations, and meets up with work in computer science, linguistics, psychology, and philosophy on the relation between conceptual, grammatical, and statistical knowledge.