We consider the influence that John Forrester’s work has had on thinking in, with, and from cases in multiple disciplines. Forrester’s essay ‘If p, Then What? Thinking in Cases’ was published in History of the Human Sciences in 1996 and transformed understandings of what a case was, and how case-based thinking worked in numerous human sciences (including, centrally, psychoanalysis). Forrester’s collection of essays Thinking in Cases was published posthumously, after his untimely death in 2015, and is the inspiration for the special issue we introduce. This comprises new research from authors working in and across the history of science and medicine, gender and sexuality studies, philosophy of science, semiotics, film studies, literary studies and comparative literature, psychoanalytic studies, medical humanities, and sociology. This research addresses what it means to reason in cases in particular temporal, spatial, or genre-focused contexts; introduces new figures (e.g. Eugène Azam, C. S. Peirce, Michael Balint) into lineages of case-based reasoning; emphasizes the unfinished and unfinishable character of some case reading and autobiographical accounts; and shows the frequency with which certain kinds of reasoning attempted with cases fail (often in instructive ways). The special issue opens up new directions for thinking and working with cases and case-based reasoning in the humanities and human sciences.