Occupational stress is the negative consequence of a distorted relation between the worker and the work environment (mental/physical load, work organisation, social relationships), where both components, that is work demands and human resources, are strictly interacting in causing more or less severe mal-adjustment and health impairment. This is mediated by several intervening factors, related not only to high cognitive and emotional stress, but also to scarce coping strategies, that are strongly influenced by personal characteristics, lack of control on working conditions, and social support. Hence high costs for the individual, the company and the whole society, not only in terms of workers' health and well-being, but also as regards work ability and performance efficiency, as well as social consequences and compensative interventions. The Occupational Health Physician has to deal with these multidimensional and multifaceted aspects of work stress by different and concurrent approaches, at both group and individual levels, with epidemiological and clinical perspectives, enacting preventive and therapeutic strategies. Both "external" work load and individual "responses" have to be properly considered and addressed not only for the evaluation of at fitness to work, but also to plan corrective actions. Hence, the OHP has to act in closer collaboration with work psychologists, sociologists, human resources managers and work organisation experts.