After graduation, medical practitioners often undertake further training in a particular field, to become a medical specialist. In North America, this is often referred to as residency training; in Commonwealth countries, such trainees are often called registrars.

In some jurisdictions, specialty training is begun immediately following completion of entry-level training, or even before. In other jurisdictions, junior medical doctors must undertake generalist (un-streamed) training for individually or enhanced years before commencing specialization. Hence, depending on jurisdiction, a specialist physician (internist) often does not achieve recognition as a specialist until twelve or further years after commencing basic medical training — five to eight years Baltimore Spine Doctor at university to obtain a basic medical qualification, and up to another six years to become a specialist.