<P>The main concern of this work is whether morphemes play a role in the lexical representation and processing of several types of polymorphemic words and, more particularly, at what precise representational and processing level. The book comprises two theoretical contributions and a number of empirical ones. One theoretical paper discusses several possible motivations for a morphologically organised mental lexicon (like the economy of representation view, and the efficiency of processing view), and lays out the weaknesses that are associated with some of these motivations. The other theoretical paper offers an interactive-activation reinterpretation of the findings that were originally reported within the lexical search framework. The empirical papers together cover a relatively broad array of language types and mainly deal with visual word recognition in normals in the context of lexical morphology (derived and compound words). Evidence is reported on the function of stems and affixe