Consists of nonfiction works, including books, essays, interviews, introductions, speeches, and miscellaneous writings.

This section covers a formidable range of dates (1924-1997) and correspondents; it is in alphabetical order by correspondent name, with two exceptions: letters pertaining to Kunitz's political activism (against the Cold War, the Vietnam War, and the Gulf War), which Kunitz originally filed and remain under "Activism" and congratulatory letters he received when he was awarded the Pulitzer Prize, which are filed under "Pulitzer Prize: Letters of Congratulations." The correspondents in this series include literary figures, colleges and universities, literary institutions, magazines and literary journals, publishers, foundations, and government agencies. Some of the important literary figures include Louise Bogan, Louise Glück, Denise Levertov, Robert (Cal) Lowell, Theodore Roethke, Michael Ryan, Anne Sexton, and Allen Tate. There are letters from the colleges and universities where Kunitz taught, beginning with Bennington College and ending with Columbia University, and where Kunitz was invited to give poetry readings or lectures, such as Sarah Lawrence College and Southern Methodist University. Kunitz's activity within the literary community is also evident, as there is a large amount of correspondence from such institutions as the Academy of American Poets, American Academy and Institute of Arts and Letters, Cathedral Church of St. John the Divine, the Poetry Center (YMHA), New York City, and the Poets House, to name just a few. Kunitz corresponded with magazines and literary journals like The American Poetry Review, The Dial , the New Yorker, Poetry , and Poetry Northwest . The Atlantic Monthly correspondence is filed under the headings "Atlantic Monthly Press" and "Davison, Peter." The correspondence (all of it) from Peter Davison was filed under his name because he is an important literary figure, not simply Kunitz's editor; however, letters from such figures as Stephen Berg and Marianne Moore, (and there are others) are located in at least two (2) places. That is, letters from Berg can be found under "American Poetry Review" and "Berg, Stephen," and Marianne Moore's letters under "(The) Dial" and "Moore, Marianne." Cases such as these are usually noted on the corresponding folders. There are also letters from Kunitz's various publishers, including Little, Brown (see also "Atlantic Monthly Press"), Martin, Secker and Warburg, and Sheep Meadow Press. There is a fair amount of correspondence from Yale University Press relating to Kunitz's responsibilities as editor of the Yale Series of Younger Poets. This sub-series also contains correspondence from various foundations, such as the John Simon Guggenheim Memorial Foundation (this includes Kunitz's fellowship application materials and letters of recommendation for some of his students) and the New Hope Foundations (see also "Marshall, Lenore G. and James"). Correspondence from government agencies pertain mostly to various cultural exchange programs in which Kunitz participated (for example, see "United States International Communication Agency"). Some other notes of interest include letters from Boni and Liveright, Publishers, whom Kunitz apparently attempted to sway to publish the prison letters of Sacco and Vanzetti, and a letter from Viking Press rejecting Kunitz's Pulitzer-Prize winning book.

Consists mostly of correspondence pertaining to the reference books that Kunitz edited for the H. W. Wilson Company but also contains some other materials related to these same books, which are interfiled with the correspondence. The sub-series ranges in dates from 1927 through 1995, with the bulk of material ranging from 1933 to 1934 and from 1952 to around 1978. For the 1933 Authors Today and Yesterday , Kunitz received a great deal of correspondence directly from the authors who were profiled in the book. These letters are in the 1933 folders and are arranged alphabetically by author name, as opposed to being arranged in chronological order by month and day.