This subseries includes correspondence from various contributors, subscribers, and collaborators, regarding the publication of Form and related projects. Correspondence is primarily addressed to Philip Steadman, although some letters are addressed to other editors or to the magazine in general.

Of note are extensive communications from collaborators, Ian Hamilton Finlay and Simon Cutts, regarding the magazine's balance of its sometimes conflicting academic and avant-garde leanings, as well as from Charles Biederman, to whom Form 3 was largely dedicated. Also notable is a letter from Brazilian concrete poet Augusto de Campos to Philip Steadman, giving directions as to the production of Campos's "cubepoem" multiple, a copy of which is present in the collection's editorial files, as well as a group of correspondence and related material from David Lyle (1899-1973), an eccentric American engineer and friend of the poet William Carlos Williams, known for his sprawling newsletter-like compositions, some of which are included in the collection.

A group of correspondence from a variety of contributors and subscribers expressing their condolences and disappointment following the demise of Form in late 1969 is also present, following the alphabetical correspondence, and includes letters from French literary theorist Roland Barthes, Bauhaus artist Xanti Schawinksy, poet and New Directions editor James Laughlin, and Fluxus artist Dick Higgins, among others.