This article describes metaphorical activity in the cognitive processes of nonfiction writers. Naturally occurring metaphors are an ongoing part of the flow of thought. It stands to reason, then, that such metaphorical activity may often underlie the abstract and literal statements nonfiction writers make in texts. To capture traces of this elusive figurative activity, periodic written thought samples were taken from 148 undergraduate writers as they composed essays. Writers who used metaphor extensively were also interviewed in order to understand metaphor's role in the writers' overall ways of working. Through the cases of three writers presented here, underlying metaphors are shown playing a generative role in shaping concepts and structuring texts. Therefore, it appears that metaphorical activity is as much a part of nonfiction writing processes as a part of fiction writing, and writers must be taught to be aware of these figurative processes. (Hildy Miller)