Impromptu speech can be defined in different ways: in terms of situational context, linguistic characteristics, and real-time processing. These approaches are not contradictory. There are certain situations that call for rapid processing of spoken discourse, and the needs of that processing are reflected in the structure of the text. The degree of "impromptuness" depends on a number of parameters including degree of scripting, extent of planning-span, and boundness to traditional macrostructural text patterns. Texts emerging from impromptu-speech situations present special problems for the linguist, who must learn to manage a host of problems often dismissed as involving performance rather than competence. One way of approaching such problems is to focus on processes involved in communication and text comprehension, and not only on the structure of texts as such. (Author/MSE)