This single case analysis of a recorded emergency call demonstrates how the categorical person reference ‘a personal doctor’ is chosen in the sequential context produced by the Medical Priority Dispatch System (MPDS) protocol, commonly used by the emergency services, to back the action in which the speaker is otherwise involved, which is to resist the sequential trajectory suggested by his interlocutor (giving instructions for cardiopulmonary resuscitation). This analysis offers a concrete throrough example of how analysts can base claims about category-bound inferences on the empirical practices of talk in interaction and it expands extant work on emergency calls by linking their sequential structure to the MPDS protocol.