The moment at which a person receives a life-threatening diagnosis is replete with drama. The life-altering impact of putting a name to disease preoccupies clinicians and social scientists, but also infuses creative work. This paper describes the use of the diagnostic moment in fiction. Using Ian McEwan’s Saturday, Anna Funder’s All That I Am, Arthur Hailey’s The Final Diagnosis, Téa Obreht’s The Tiger’s Wife, and myriad others, I show how diagnosis is variably the subject, the trigger, and the frame for narratives. It is a characterization device as well as a tool for defining right and wrong, morality and truth. But it is also a means by which we can “imagine” diagnosis, ahead of any experience of illness, and give meaning to what a serious diagnosis may mean in the life of an individual.