The author describes the operating course of the Occupational Medicine Operating Units (OMOU) in our region. (Lombardia) These Units, born as a second level support to the Basal Occupational Medicine Units, greatly enlarged, as time passed, the limits of their users together with the charge of preventive duties ordered to the employers by the recent laws regarding Occupational Hygiene. (DLgs 277/91-DLgs 626/94) The author also illustrates the variety of the diagnostic demands to the OMOU according to the enlargement of the legal protection of occupational diseases and to the numerous aspects of specific job fitness. He underlines the need of multiple specialistic skillfulnesses achievable by means of a complete integration of OMOU in to the hospital to which they belong. In conclusion the author illustrates the new tasks of the OMOU in the field of the therapy and rehabilitation.