This paper examines the relationship between unemployment duration before entry into active labor market programs and their effects on individual reemployment probabilities. For this purpose, we develop a general framework for the evaluation problem with multiple treatments and varying dates of entry into treatments. Our application is concerned with the youth employment programs which were set up in France during the last twenty years. The empirical analysis makes use of two nonexperimental data sets collected over two different periods, 1986-1988 and 1995-1998. Results show that long-term unemployed young workers benefited from different types of programs over the two subperiods.