This paper describes an integrated approach for interpreting a user’s responses and generating replies in the framework of a WWW-based Bayesian argumentation system. Our system consults a user model which represents a user’s beliefs, inferences and attentional focus, as well as the system’s certainty regarding the user’s beliefs. The interpretation mechanism takes into account these factors to infer the intended effect of the user’s response on the system’s argument. The reply-generation mechanism focuses on the identification of discrepancies between the beliefs in the user model and the beliefs held by the system that are relevant to the inferred interpretation.