--- - |2 Diagnosis is rarely a straightforward process. This is especially so in psychiatry, where diagnoses are not based on organic biomarkers (e.g., blood tests). Diagnosis can be particularly complicated for children, whose symptoms must be disentangled from typical developmental processes. In this paper, we examine how clinicians use narrative as a method for differentiating a child's autism from a possible co‐morbid seizure disorder. Our approach is conversation analysis, and we show that narrative is a pervasive and endogenous practice for producing warrantable diagnostic knowledge about patients and, as such, forms part of what we term “the practical epistemology of clinical work.” - Symbolic Interaction, Volume 41, Issue 3, Page 357-383, August 2018.