This article aims to assess how occupational health became a topic of mobilizations and debates during the “1968 years” in France. In this period, workers demanded a better way of preventing occupational diseases. At that time medical power had scarcely been criticized, and some medical practitioners helped workers in their fight to prevent occupational disease. Dealing with the example of lead poisoning and a case of mobilization in the French Peñarroya plant near Lyon, this article analyzes how new social actors, mainly workers and committed medical practitioners, managed to set up and promote an earlier screening of this occupational disease. It sheds light on a new medical appraisal process, which has stemmed from continuing debates between workers and medical practitioners. This process produced a counter-knowledge that effectively challenged the productive order in this plant and official occupational medicine as well.