This dissertation re-evaluates the place of José Donoso in the Latin American Boom as well as the consequences of this period in the writing process of his most renowned novel, The Obscene Bird of Night (1970). Its focal points are under-utilized archival material related to the novel's writing process, including Donoso's notebooks, typescripts and his personal correspondence. Spotlighting the transformation of specific episodes of the novel and the traces of the Boom through his notebooks, I argue that the published version of this work is in great part the result of Donoso's relationships with the writers of the Boom and the "nueva novela". The borderline position that Donoso occupies in the Boom (sometimes included, sometimes not) can best be explained by the late publication of this crucial novel, since Donoso's correspondence reveals that he was an important agent in the machinery behind the Boom.