This article's purpose is to address a hitherto unexplored topic in the history of education: the story of the "Cátedras Ambulantes," officially referred to as "Misiones Pedagógicas" during the final years of the Franco dictatorship and the beginning of the transition to democracy (1966-1977). The study is based on a historical-educational methodology, triangulating through the following sources: a dedicated bibliography; all kinds of press releases, reports and official circulars issued by related agencies; the main Orders, Decrees and Laws within which they were framed by Spanish legislation at that time; and, finally, contemporary press reports. The results reveal the origin, nature and evolution of these 50 itinerant classrooms, "Cátedras-Misiones Pedagógicas," in terms of legislation, the training received by the state-registered teachers (mostly women) responsible for the classes, the difficulties that arose, and the main criticisms and issues they attracted (1966-1977).