Correspondence, manuscripts, notes, notebooks, documents, photographs, course-related materials, and printed materials. The manuscripts include typescripts of Sykes' published and unpublished novels, monographs, plays, short stories, and articles. Among these are The Perennial Avant Garde, The Cool Millennium, and The Hidden Remnant. Sykes' notes and notebooks span the period from the early 1930s to 1980, and include preliminary ideas and sketches for his books, as well as autobiographical material. A small number of documents concern Sykes' wartime work in the U.S. Government Office of War Information. Course-related material including writings and correspondence of students taught by Sykes between 1962 and 1975 at the New School and as an adjunct professor at Columbia University. Printed materials consist of numerous reviews of Sykes' books, in addition to offprints and articles by Sykes. Included as well are printed materials about or connected with Sykes, offprints of articles inscribed to him, and many volumes from his library. The substantial correspondence series includes personal letters and correspondence with agents and publishers relating to his books. Correspondents include Harold Clurman, Aaron Copland, Lawrence Durrell, Georgia O'Keeffe, and Francis Steegmuller, as well as a number of Sykes' students. There is extensive correspondence between Sykes and the artist John Hartell from 1927 to 1983.

Correspondence, manuscripts, subject files and research notes of Sigmund Diamond. Included among the correspondence are Diamond's letters to and from various distinguished members of Columbia University and other academic insitutions, as well as correspondence with many noted sociologists and historians. Included in the manuscripts is Diamond's "In Quest." The subject files comprise material from Diamond's tenure at Columbia and include some material pertaining to his forced departure from Harvard in the 1950's due to his previous communist affiliation, and his active role in maintaining the efficacy of the Freedom of Information Act. The research files include microfilms and notes.