Two letters written by James Y. Simpson are included among a bound collection of 25 of his pamphlets held in the Gordon Craig Collection of the Library of the Royal Australasian College of Surgeons. Both letters are written in pamphlets relating to Simpson's championing of chloroform. The first letter is written in a proof copy of a pamphlet titled Notice of a new anaesthetic agent as a substitute for Sulphuric ether in Surgery and Midwifery. This very rare pamphlet was posted to Dr Fleetwood Churchill, a Dublin obstetrician, on 13 November 1847, 9 days after the 'dining room experiment' in Simpson' s home, when the anaesthetic properties of chloroform were dramatically demonstrated. The second letter is written 10 months later and is also addressed to Dr Fleetwood Churchill. The content of both letters is discussed, as is also the rarity of the proof copies of the first printed document describing the use of chloroform.