Analysis of naturally occurring information- seeking dialogues indicates that information providers often query a user when there is insuffi- cient information to formulate a plan that satisfies the user's intentions. In this paper, we present a mechanism that determines when queries are re- quired to elicit additional information from a user and the manner in which these queries should be posed. Query generation is done by taking into account the amount of relevant information in the user's intentions eis recognized by a plan recogni- tion mechanism. The mechanism for query gen- eration described in this paper has been imple- mented as a component of a computerized infor- mation providing system in the travel domain.