Wilfrid Lawson (Dustman with Cyst) and Bernard Miles (Haymaking Farmer) refused to do publicity for this movie.
The role of matron was offered to Joan Sims but she turned it down saying that no one could do it better than Hattie Jacques.
Geoffrey Keen, Martin Benson and Shirley Eaton would all go on to make appearances in the James Bond film franchise.
Richard Gordon: The author of the original books (and of the screenplay here) is on-screen, hidden behind the anaesthetist's mask in the "patient wakes up" scene. Gordon did the job in real-life before turning to writing.