Doctors must go through a new system of checks to show they are safe to treat patients as of today.
Some 19,373 doctors registered and licensed to work in Scotland will be taking part in so-called "revalidation" procedures being brought in across the UK.
The new system makes regular revalidation, usually every five years, a requirement for all doctors to keep their licences.
Run by the General Medical Council (GMC), the system is based on each doctor having an annual appraisal and, on a five-yearly basis, submitting to feedback from patients, fellow doctors, nurses and other colleagues. This is intended to demonstrate they are fit to practise and keeping up-to-date with medical advances.
Though many doctors across the UK already have annual appraisals, concerns have been raised about the patchy way they have been carried out up until now.
The new checks will apply to all doctors, including GPs, hospital doctors, locums and those working in the independent sector. The UK is the first country in the world to introduce such a system.
The GMC said it expected to revalidate the majority of licensed doctors by March 2016, with medical leaders expected to go first.
Professor Sir Peter Rubin, chairman of the GMC, said: "This is an important day for doctors and patients. We are confident that, over time, revalidation will make a significant contribution to the quality of care that patients receive and should give them increased confidence that the doctors who treat them are up-to-date."
Margaret Watt, chairwoman of the Scotland Patients Association, said: "This system will prove a doctor is fit to carry on as a doctor. It's long overdue: there should be some sort of revalidation to ensure they are maintaining the expertise they gained at university and to make sure they are keeping up to speed with medical developments as well."
A Scottish Government spokesperson said: "This is a significant step for the medical profession, and will make an important contribution to the safety of patients and the quality of care they receive."