Occupational medicine is actually not a sub-specialty of internal medicine, although there are currently a lot of internists working as occupational physicians since it's such a new specialty. I think that occupational medicine residency takes some 4 yrs to complete, most offer you an MPH as part of completing the residency too. Salary is 140-180 K, depending on where you work. Hours are really nice, no call, regular business hours (if that). There is a lot of stress associated with being an occupational medicine, there bound to be a lot of friction between you, the employees, and the employer, since everyone want's something. Employees want more time off for back pain, while the employers want employees to work. A lot of it is mediation and being political. Also, sometimes you have to inform employees and their managers if they test positive for drugs or can no longer safely function at their job, and this can cause a lot of conflict too. There was an article in a local paper around here about how the city employee physician always had to have a security guard on duty outside of her office because of all the death threats she has been getting since getting some employees fired and cutting down on employee sick days. People have also been slashing her tires too. Some people just like to shoot the messenger I guess.