SUMMARY In 1900, a special type of unemployment insurance was set up in Belgium: the so-called “Ghent system”, which had some influence on the development of unemployment insurance in many European countries. This particular system was characterized by the important role played by the trade-union unemployment societies. The public authorities (in Belgium, from 1920 onwards, the central government next to the towns and provinces) encouraged the affiliation of the labourers to these societies by granting different sorts of financial support to the unemployed society members and to the societies themselves. During the crisis of the 1930s, this led to an important growth of Belgian trade-union membership. On the other hand, the quantitative growth of the labour movement due to this particular organization of unemployment insurance, led to many negative sideeffects for the trade unions (administrative chaos, financial problems, loss of combativity). Moreover, the employers' organizations strongly opposed this system of unemployment insurance, because they thought it reinforced the labour movement's power in society (strengthening of union membership, influence on wage formation, obstruction of deflation policy). This article examines the heated debates waged in the labour movement itself and between this actor, the employers' organizations and the government, to solve the many important problems posed by this type of social insurance. The Belgian pre-Second World War debate concerning unemployment insurance was of great importance for the shaping of the Welfare State in Belgium, which took its present-day form in 1944.