Finding an explanation for the rise and persistence of European unemployment has been one of the main research programmes of labour economists during the last decade. In this doctoral thesis, we contribute to this literature by questioning the causes of unemployment persistence in Belgium. To that purpose, we conduct an in-depth econometric analysis of the flows out of unemployment in this country. In Chapters 2 and 3, we study the behaviour of the exit rate out of unemployment over duration and calendar time. In Chapter 3, we investigate whether this behaviour differs according to the place of living and the skill level, as measured by the level of education. Finally, in Chapter 4, we determine to what extent the divergences in the rate of flowing from unemployment between workers with different levels of education can be explained by a skill mismatch phenomenon and/or by a job competition story. By refining the causes of unemployment persistence in Belgium, our doctoral research also contributes to the design of more effective labour market policies. ; (ECON 3)--UCL, 2002