Resumen: Este texto analiza las actividades de la Delegación Especial para la Información de Residentes en Territorio Liberado (DIDREM), una organización en funcionamiento durante los años de la Guerra Civil (1936Civil ( -1939, conformada por personal voluntario, formalmente destinada a recabar información sobre las personas que se encontraban en Madrid y, con posterioridad, en el resto del territorio sometido por las tropas franquistas y cuyos datos fueron empleados con fines represores, ya durante la guerra y, particularmente, al finalizar ésta.Palabras clave: Guerra Civil, Franquismo, Espionaje, Represión, Acción Católica, DIDREM. between publicity and espionage: the special delegation for information of residents of liberated territory (didrem) in spanish civil War (1936War ( -1939 Abstract: This article examines the activities of the Special Delegation for Information of Residents of Liberated Territory (DIDREM), an organization operating in the years of the Spanish Civil War (1936)(1937)(1938)(1939), formed by volunteers, formally intended to gather information on people who were in Madrid and, later, in the rest of the territory subdued by Franco's troops; the data were used with repressive purposes, during the war and, particularly, at the end of it.