In this paper we examine the pragmatic knowledge an utterance-planning system must have in order to produce certain kinds of definite and indefinite noun phrases. An system, like other planning systems, plans actions to satisfy an agent's goals, but allows some of the actions to consist of the utterance of sentences. This approach to language generation emphasizes the view of language as action, and hence assigns a critical role to pragmatics. The noun phrases under consideration in this paper are those that presuppose the existence of an individual that could be described by the description D. In other.