The paper considers changes in occupational medicine in the last fifty years, describes industrial hygienists tasks and the reasons why their activities grew in importance. Also the needs of compliance with their own professional Code of Ethics are discussed. The Universal Declaration of Human Rights, voted and accepted by the United Nations in 1948 changed the strategic target of occupational medicine. Since then the most important task became prevention of health damage caused by work, which should enable the employees to stay healthy throughout the whole period of professional activity. Before that the main target was to restore the health of employees injured by work. To make the used preventive measures to be effective, they must be selected appropriately to professional harmfulness posing threat to employees health. This requires to reveal all factors potentially harmful to health, which occur in the work-environment, to measure their concentrations or intensity, to determine the employees exposure to those factors and to estimate the level of the health risk, caused by this complex exposure. Contemporarily occupational medicine service encompass with its preventive supervision the municipal environments, because they become seriously polluted due to emission of harmful industrial pollutants what brings about a negative impact to health of exposed dwellers. Those activities, being to a large extent outside the scope of competence and tasks of doctors – specialists of occupational medicine, are performed by industrial hygienists, who the required knowledge and skills acquired during university studies on technical and natural faculties. This caused a substantial increase of the role of industrial hygienists in the present activity of occupational medicine service and simultaneously took into consideration the ethical aspects of the work of these professionals. Evaluation of the backbone and the scope of work drew attention not only to the need to follow ethical principles mandatory for everybody working in occupational medicine service but also to the need to have and respect their own ethical code taking into account the specificity of activities and undertaken tasks in this profession.