OBJECTIVE: To describe trends and developments in the total duration of training medical specialists in the Netherlands, including their ages upon completion of the components of medical education: undergraduate medical program, waiting time and further post-graduate specialist training.DESIGN: Population cohort study.METHOD: From the combined data from Statistics Netherlands and the Registration Committee for Medical Specialists for the period 1986 to 2018 relevant populations were selected and training trajectories were mapped. The population size was 40,604 individuals for undergraduate medical programs, 41,885 for the duration of post-graduate specialist training, 31,915 for the waiting periods and 21666 for the total duration of the trajectory from the start of medical school until registration as a specialist.RESULTS: The median duration of undergraduate medical programs was 7.1 years, which is longer than the nominal duration and this remained unchanged over the observation period. The average waiting time between graduating medical school and postgraduate specialist training has increased from 2010 onwards to 3.7 years in 2018. The average duration of postgraduate specialist training is increasing. The average age at graduation of medical school fell by 1.7 years to 26.1. The average age at the start of post-graduate specialist training decreased, as did the average age at registration as a specialist.CONCLUSION: The total duration of training of medical specialists is stable. Changes such as "dedicated transition year" and flexible arrangements for postgraduate training have had no discernible influence on the total duration of medical training. Because the average age at start of postgraduate specialist training has decreased, medical specialists are on average younger upon registration.</p