What is the correct salutation for a doctor?

A GP is called doctor

A Specialist is called Mister

Answer A specialist surgeon* is called mister, at least in Britain, Australia and NZ. All other medical specialists are called doctor. This dates back to barber-surgeons in the Royal Navy, who were not officers so their salutation "mister" elevated them above most of the crew and made them "honorary officers".

*A specialist surgeon (orthopaedic, thoracic, cardio-vascular etc) in these countries has to be a member of the country's College of Surgeons (i.e Fellow of the Royal College of Surgeons (FRCS), FRACS, FRNZCS).