Although explanations of the persistence of high unemployment in Germany, in particular long-term unemployment, have increasingly focused on structural factors, there is only very limited evidence on their empirical importance so far. In this paper, these factors are analyzed based on a microeconometric model of individual transitions from unemployment into employment and non-participation for the West German labour market. The empirical analysis is based on waves 1 - 9 of the Socio-Economic Panel for West Germany covering the period 1983 to 1992. The focus of the study is on the importance of 'negative duration dependence' arising from causal factors and 'sorting' effects due to unobserved heterogeneity in the unemployment pool. I also sort out the relative contribution of various factors, such as individual characteristics, the state of the labour market, and the effects of unemployment benefits on long-term unemployment.