In this chapter we will consider the in¯uence of a range of lexical and semantic variables on short-term memory (immediate serial recall) tasks. The term ``lexical variables'' refers to word properties, such as word frequency and concreteness, which re¯ect differences in the way in which words are represented in ``long-term'' or lexical memory. The fact that such lexical variables in¯uence short-term memory tasks provides prima facie evidence that such tasks depend critically upon long-term memory representations, or more radically, that the fractionation of memory into shortand long-term stores may be unnecessary. We begin by describing the historical development of our own ideas, in the context of the trace decay models that have dominated the latter half of the twentieth century. Our primary aim is to show the in¯uences and development of the redintegration model (Hulme, Roodenrys, Schweickert, Brown, Martin, & Stuart, 1997). However in the process, we will acknowledge parallel developments in other models. After outlining some of the major ®ndings in the area, we draw out their theoretical implications and describe some of those models that have begun to take into account these ®ndings.