The occupational physician, performing health surveillance within a hospital, may face to some difficulties due to the variety and complexity of the tasks and the health risk factors of the health care workers. One of the hardest issue for occupational physician is to provide judgement on worker's fitness. Moreover, this task could be more complicated when a impaired worker could represent an hazard for his patients and colleagues. The authors will illustrate three critical clinical cases examined in Occupational Health Unit of Luigi Sacco Hospital, Milan; furthermore, the authors will show the difficulties and the applied solutions in order to provide the judgement on worker's fitness.