The series consists of chiefly of letters written by Osler that Cushing collecting during the preparation of his biography, The Life of Sir William Osler, between the years of 1920 and 1924. The letters in the series include both originals and transcriptions. The series also contains accompanying notes (both by Cushing and by Osler), clippings, articles, and other ephemera related to Osler.

This series contains working papers, notes, drafts, articles, and ephemera compiled by Cushing during the preparation of his biography of Sir William Osler. The material is arranged alphabetically generally by topic or author. There are also two files of Cushing's correspondence related to the publication of the biography.

This series contains of Cushing's typewritten drafts of chapters from his book, The Life of Sir William Osler. The series is arranged into files corresponding to chapter divisions.