Series contains both personal and professional correspondence between Ryan and family members, friends, collaborators, and other colleagues. Professional correspondence is found with Myrdene Anderson, Peter Berg of Planet Drum, Morris Berman, Avery Johnson, Jack Burnham, Red Burns, Bob Harris, Marga Bijvoet, Thomas Berry, Lois Biachi, David Dunn, Roberta Kevelson, Gerrit Lansing, Oliver Lowenstein, Aldo Lira, Chip Lord, Claude Ponsol, Jody Procter, Jodi Sibert, Phyllis Gershuny Segura, Michael Shamberg, Marita Sturken, and Howard Wise. Corporate correspondence is found regarding job applications, manuscript submissions to publishers, and video submissions to museums and broadcasters.

Correspondence is arranged alphabetically. Letters regarding institutional relationship with Ryan filed by corporate name; otherwise letters are filed by personal name. Correspondents with 3 or more letters have their own folders. Otherwise letters are filed in a general alphabetical file. Significant correspondents in general files are noted in the folder listing. Where outgoing letters written by Ran were found alongside incoming letters, the outgoing and incoming letters are kept together under correspondent's name. Otherwise, Ryan's outgoing letters and drafts of letters are filed chronologically under Ryan's name. Letters signed only with first names, unsigned, and illegibly signed letters are filed at the end of the series.

Letters from Ryan to his family during his years in the monastery (1960-1964) are found in series 1, Biographical materials, as are letters among Ryan's family members written before he was born. Additional correspondence concerning Ryan's professional life is found in Series 4, Organizational Records, Series 5, Projects, and Series 6, Teaching Files.