Incoming and outgoing manuscript and typescript letters, carbons, telegrams, and postcards generated during Anderson's career. Series I is arranged alphabetically by correspondent's name and then chronologically within each folder.

When correspondence files include letters to a third party (i.e., not Anderson), the name is indicated on the container list, indented under the folder title.

Unidentified correspondence has been filed as "Unidentified" and is arranged chronologically. Enclosed manuscripts have been removed from this series and placed in Series IV or V as appropriate. As with the reprints, a photocopy of the title page was filed with the original letter. Cross-references are also given for enclosed photographs, which have been removed to Series VII. Letters of reference are filed under the name of the person who is the subject of the letter.

The bulk of this series covers the 1950s to the 1960s. Correspondents include biophysicists, biochemists, geneticists, students, and publishers. Among the topics covered in this series are biological electron microscopy; research on bacterial viruses; conferences; the publishing of journal articles; and participation in professional societies. There is correspondence about Anderson's affiliations with the Biophysical Society, Electron Microscope Society of America, International Committee on Nomenclature of Viruses, International Union for Pure and Applied Biophysics, and the Philadelphia Electron Microscope Society. There is also correspondence concerning his work at The Institute for Cancer Research, the Institute for Medical Research, RCA Laboratories, and the University of Pennsylvania.

Correspondents in Series I include:

Anderson's bibliography and curriculum vitae; some biographical material about Anderson; newspaper clippings; material about conferences; calendars/daybooks for almost every year from 1941 to 1989 that contain Anderson's brief notes; letters written by colleagues and publishers asking for Anderson's permission to publish electron micrographs taken by him; a guest register used in 1942 and in 1949 at the Marine Biological Laboratory in Woods Hole, Massachusetts; and meeting minutes, agenda, and reports for the Biophysical Society. The folders are arranged alphabetically by title.

Applications, reports, correspondence, and expenditure statements for various agencies that granted Anderson research money for his laboratories at the University of Pennsylvania's Johnson Foundation and at The Institute for Cancer Research. The United States Office of Naval Research accounts for a large portion of the material. Other granting agencies include the National Cancer Institute, the National Science Foundation, and the United States Atomic Energy Commission. There are two folders of material about the National Research Council's RCA Fellowship that Anderson received in 1940.

Also in this series are reviews of other people's grant applications that Anderson wrote for various agencies, including the National Institutes of Health, the National Research Council, the National Science Foundation, and the United States Atomic Energy Commission. The folders are arranged alphabetically by title.

Anderson's typewritten and handwritten outlines, preparatory notes, research, graphs and figures, drafts, and some galley proofs for articles. There are some notes for lectures, as well as several reviews of books. Some of the works are co-authored with colleagues and students. For each work, the notes and drafts are filed together. This series includes several early papers from the 1930s; the earliest is an article in German, "Ein Neues Drehprismenverfahren zur Photographischen Ermittlung der Dispersion. II. Mitteilung uber Refraktion und Dispersion von Kristallen," from 1935. There are also several historical treatments of electron microscopy, including "The First Years of the Electron Microscope in the United States, 1940-52," "Reflections on Phage Genetics," and Anderson's biographical memoir of Jack Schultz ("Jack Schultz, May 7, 1904 - April 29, 1971"). This series is arranged alphabetically by title, and cross references are given for photographs that appear in the series.

Articles, notes, reports, and abstracts written by colleagues and students of Anderson. Some authors are represented by two or more manuscripts, including Helen Gay, Hartmut Hoffmann-Berling, François Jacob, Andrzej W. Kozinski, Bruce R. Levin, Peter C. Nowell, Jonathan T. Ou, Lee D. Simon, Donald H. Walker, Jr., and Nobuto Yamamoto. Most of the works are scientific in nature, although there are two historical articles by Lily E. Kay. Any works that Anderson co-wrote with students and colleagues are filed in Series III alphabetically by title. Cross references are given for photographs that appear in this series.

Loose notes and notebooks that are arranged by folder title and include notes from experiments (e.g, "Growth Requirements of T2, T4A, T6"); notes taken by Anderson at Cold Spring Harbor and at other symposia; and course notes from Anderson's days at California Institute of Technology (e.g., "Atomic Physics"). Notebooks with no title have been filed as "Unidentified--Notebook." Some notebooks have loose notes that are larger than the notebook pages. These notes were placed in the same folder as the notebook but at the end of the folder. A photocopy of the first sheet of notes was placed at the appropriate notebook page with a cross reference to the end of the folder.

Prints and negatives of electron micrographs that Anderson took of viruses and Drosophila, among other specimens. Some of the micrographs were used for articles, while others are unpublished. The prints are of varying sizes, including many oversized, and many are unidentified. There are also a few photographs of Anderson and his colleagues.