We propose a theory of communicative interactions based on the idea that it is constitutive of interpersonal communication to create and manage a fragment of social reality. We define such a fragment in terms of joint commitments of the interactants, and analyze how these commitments are made in a conversation. We distinguish between three layers of joint commitments: those that regulate the embedding activity of the conversation; those that constitute the joint meaning of communicative acts; and those that concern the target of the conversation. We argue that joint commitments are created in a concrete situation by producing and negotiating interper¬sonal affordances, which allows the interactants to retain suitable freedom of movement. Finally, we analyze some relationships between our conception of communicative acts and illocutionary acts.