Introduction -- Preparing the ground, sowing the seed -- World War I and the condition of labor -- A white international? -- Social Catholic analyses before 'Quadragesimo Anno' : common aims, diverse paths -- Vitality in the low countries -- France : controversies and advances -- New departures in Catholic action : youth movements in the working class -- Women's Catholic labor movements -- Christian labor in Weimar Germany -- Italy and Austria : Christian labor at grips with authoritarian rule -- 'Quadragesimo Anno, ' in 1931 : its controversial reception -- France, Belgiu, the Netherlands : Christian labor in the Depression years -- Labor and Catholicism under the impact of World War II -- Working within secular pluralism -- Conclusion