The Sir William Osler Collection, distinct from the Bibliotheca, is an extensive archival holding of Osler's correspondence (including eighteen hundred original letters), daybooks, accounts, engagement books, legal documents, book invoices, membership certificates, notebooks, lectures, addresses, newspaper clippings, photographs, books with manuscript additions, and miscellaneous loose items formerly inserted into individual books in his library. The collection also contains various family papers, including correspondence of Lady Grace Revere Osler and Edward Revere Osler.

Fonds documents the Mallochs' activities related to their medical and literary work. The fonds contains notes, correpondence, commonplace books, account books, material related to publications, family memorabilia, scrapbooks, photographs, telegrams, postcards and certificates.

The fonds contains Dr. Jacques' journal of medical accounts receivable entered in an account book issued with blank pages and bound in half suede with green cloth boards. The account book was kept between November 1879 and January 1881. A title handwritten on a paper label on the cover reads "Journal pour 1879-1880-1881." The author's full name comes from within the journal (L. A. George Jacques, M. D.) and from Lovell's Montreal directory for 1881-1882 (Louis A. George Jacques, M. D.). Laid in at p. 207 is an ink blotter featuring pharmaceutical advertising for Glyco-Heroin (Smith).

Fonds documents Frederick Augusutus Rees' activities as a physician in Bermuda. The fonds contains a ledger, an index to the ledger, notes and letters.

Fonds contains the financial records of A.R.V. White for his years of private practice. It includes journals, cash books, ledgers and receipts relating to his income and expenditure for his practice in Stanstead, as well as records relating to his bonds and stocks. The fonds contains thirty volumes entitled Journal, Cash book and Ledger filed by year from 1935 to 1964, and a file with loose inserts .

Fonds shows Dr. Allan McMillan's activities as a country doctor in the Eastern Townships of the end of the 19th century. |a The fonds consists of 6 daybooks separated into 6 vols.: v. 1: 22 Apr. 1876-18 Sept. 1885, v. 2: 22 Sept. 1885-7 March 1887, v. 3: 15 March 1894-24 Feb. 1897, v. 4: 1 Aug. 1898-30 June 1900, v. 5: 1 July 1900-8 June 1905, v. 6: 12 June 1905-14 July 1908.