This article examines patients’ answers to doctors’ questions during history taking as a central activity format which reveal a deeper understanding of each other. An analysis of medical interactions shows that patients mostly expand the topical, structural and/or pragmatic scope of their questions. The sequential positioning of answers provides more possibilities than is to be seen from a strict perspective of question types. Patients’ answers reflect their understanding of the current interaction type, and of the question’s implications, doctors’ relevancies as patients assume them, or even the doctors’ presupposed next question; a phenomenon we call anticipatory reaction. Both action formats and their interplay point to two important principles of interaction: the principle of cooperation and the principle of progressivity within the frame of the particular interaction type.