Benedict Anderson and Ruth McVey’s legendary publication, A Preliminary Analysis of the October 1, 1965, Coup in Indonesia, was completed in January 1966 and shared at that time with fewer than two dozen individuals. It was not published formally until 1971. Nevertheless, the paper’s contents leaked in early 1966 and its line of analysis elicited great interest worldwide among diplomats, journalists, and academics, long before most observers could have seen a copy. While the essay and its conclusions have been the subject of intense scholarly and political debate and criticism, little attention has been paid to how a confidential paper by respected Cornell University scholars gained such notoriety and prompted so much anxiety. This article explores the social history of the so-called “Cornell Paper” (including common theories about the leak) and examines the paper’s relationship to Anderson’s scholarship on Indonesia more generally and whether Anderson’s views about the events of October 1, 1965, changed over time.