Abstract: Numerous letters appear on stage in Spanish Golden Age theatre with Lope de Vega or Calderón de la Barca. Besides its significance for the dénouement of the dramatic action, the letter can also have a comic, verbal, and situational function. The presence of the figure of the secretary only reinforces the reality effect, especially when the letter is composed in prose, which provokes a contrast with the conventions of Spanish theatre of the time, which was always in verse.