This article analyses contemporary changes in the production of knowledge and expertise pertaining to occupational health, by relating them to the characteristics of this public policy sector and recent developments within it. The article first shows how changes in public health policy necessarily induce certain changes in occupational health, for instance by making the creation of new expert agencies mandatory. It then examines the institutionalization of expertise on occupational risks, along with the impact this has on the modalities of decision making in a specific field. It explains that in spite of huge changes, the power relations characterizing this public policy domain remain relatively stable. Finally, apart from the case of occupational health, this article raises the question again of the production for knowledge and expertise, by relating them to the power plays structuring a public policy sector.