Discourse markers, also known as cue words, are used extensively in human-human task-oriented dialogs to signal the structure of the discourse. Previous work showed their importance in monologues for marking discourse structure, but little attention has been paid to their importance in spoken dialog systems. This paper investigates what discourse markers signal about the up- coming speech, and when they tend to be used in task-oriented dialog. We demonstrate that there is a high correlation between specific discourse markers and specific conversational moves, between discourse marker use and adjacency pairs, and between discourse markers and the speaker's orientation to information presented in the prior turn.