RESUMEN
Health surveillance has its well defined place within occupational health care. Only a few functions are specific to the chemical industry. Occupational health surveillance used to be targeted at the early detection of occupational illnesses (secondary prevention) but other purposes have gained importance in recent years: ensuring the fitness of every worker for his or her job, promoting workers' health in general, contributing to the safety of the plant operation by identifying workers whose behaviour is likely to endanger others, contributing to product quality by assisting in the fulfilment of good manufacturing practice requirements, etc. If the occupational physician wants to maintain his role as key player in protecting workers' health, he must get involved in the important activities of primary prevention contributing directly to workplace improvements. Such improvements can only be based on systematic assessments of the workplaces. These assessments again provide the necessary objective basis to structure health surveillance in a way that takes into account the possible adverse effects coming from the workplace.