The 1930 law creating social insurance was the Third Republic's great achievement in the social arena. However, the historiography of contemporary France contains barely a trace of this achievement. Victim of the regime's discredit as well as of the lack of any reformist political efforts in its favor, social insurance of the 1930s has also suffered by comparison to later achievements, particularly the creation of Social Security in 1945. However, if we study social insurance in its own historical context—and not in reference to the postwar period—, it can constitute an original source for the study of the modernization of French society. This article proposes three approaches: social insurance constitutes a vector for the acculturation of the working class to retirement and to the medicalization of health, contributing to the history of working class uses and representations of consumption and social rights. On a more institutional level, the experience of social insurance reveals the first legal experiments with co-gestion involving employers, workers, and insurance organizations. Finally, a prosopographical study of the militant trajectories linked to social insurance could contribute to the history of the working-class movement between 1930 and the end of the Thirty Glorious Years: is there a "social insurance generation" within French syndicalism?