This paper examines Italy's worker-based model for occupational health, especially its key concepts and its relation to social conflict. It briefly reviews the history of three approaches to occupational health in Italy: university-based, industry-based, and government-based. It then analyzes the worker-based approach, which emerged in the late 1960s and early 1970s as worker groups and trade unions mobilized around new concepts of occupational health. Five key concepts are discussed: the workers' homogeneous group; workers' subjectivity; the use of contract language; the development of local occupational health institutions; and the use of occupational hazard risk maps. The analysis illustrates how the social processes of mobilization and institutionalization affected the ideas and structures of Italian occupational health. Worker mobilization in Italy produced ideological changes in the nation's occupational health system, institutional changes in universities and governments, and legislative changes at national and local levels. The institutionalization of reforms, however, created new conflicts and problems and tended to restrict worker participation and promote expert intervention. The paper concludes with a brief outline of the history of occupational health approaches in the United States and then discusses the implications of the five Italian concepts for US occupational health policy.