The definition of occupational health has changed significantly over time to cover broader aspects of health care and to promote worker's health. Over the centuries, the relationship between workplace hazards and occupational health care has been influenced by the character of work, social evolution and changes in manufacture, economy and demographics of the working populations. Numerous old civilizations showed deep prejudice towards human work. Very often manual work was done by slaves, and their health and safety were neglected. A spectrum of occupational diseases (acute, chronic, malignant and damage of reproduction) cover all organic body system, each of which can be affected by exposure to specific agents at workplace. Work and working conditions may deteriorate and worsen an existing illness which is not necessarily work-related. Living habits may also interfere with occupational factors leading to the development of a disease. Today, occupational medicine is the only medical field encompassing occupation and environment and health. This article also describes the historic development of occupational medicine in Croatia and some of the current regulations on occupational health in the country.