While the Vlaams Blok (currently Vlaams Belang) became one of the most successful and electorally durable extreme-right parties in Europe in the 1990s, the francophone Front National has yet to achieve a stable basis of support. We argue that an important reason for this divergence has been the behaviour of Social Democratic parties in the two regions of Belgium. In Wallonia, the Parti Socialiste (PS) held onto its traditional electorate through both distributing material benefits and by keeping traditional economic themes, or issues that it ‘owns’, high on the political agenda. The SP (currently SP.A) in Flanders has done less well on both counts. Since Social Democratic parties across Western Europe have lost voters to the extreme right, our comparison suggests that their behaviour is an important variable in understanding cross-national variation in the extreme-right’s success.