This article describes the dialog module of EVAR. The dialog is seen as a sequence of dialog acts uttered by the system and the user. From a corpus of real human-human dialogs a model was extracted. The model covers all sequences of dialog acts observed in the corpus. Each dialog act is modelled as a set of pragmatic, semantic and syntactic concepts. The properties of the concepts and the current dialog state are used to identify the actual dialog act. Each user utterance is interpreted by the system and the system reacts with the appropriate dialog act. After the user has defined his request completly, the system starts a database query and finally generates a synthesized natural language answer. The answer generation is realised with sentence masks, where the information from the database enquiry is filled in at the appropriate slots. A dialog memory which allows the interpretation of elliptical sentences and proforms is updated after each utterance.