This chapter attempts to review electrophysiological data that stand at the intersection of two large domains of research: selective attention and semantic processing. Analogous behavioral studies will be discussed as a way of introducing the reader to some of the more complex paradigms, and providing convergent evidence. The focus of this review will be on data that add special insight into the issue of semantic processing in the absence of attention. However, paradigms which allow semantic activation in the absence of awareness will also be examined as these studies have also yielded data concerning automatic semantic processing. It is concluded that a great deal of semantic processing can occur in the absence of attention as well as in the absence of awareness.