Abstract : This PhD dissertation provides useful empirical contributions for two research topics about flexicurity: the use of the short-time compensation (STC) program by French establishments and the role of the three "bases" of flexicurity - employment contract, skills and territory (Freyssinet, 2006) - in making professional career paths secure. About the first topic, we develop a methodology to analyse the efficiency of STC and to verify if it could be considered as a flexicurity tool. According to two efficiency criteria (avoiding redundancies and establishment exit), STC does not protect employment and so it is inefficient: Between 1995 and 2005, it represents mainly a flexibility tool. It can not been seen as a tool responding to the principles of flexicurity. In the line of the second topic, we analyse how the "bases" of flexicurity make professional career paths secure, by focusing on three professional mobilities: first employment-employment, employment-employment and unemployment-employment. We show the importance of temporary contracts, firm networks and individual's place of residence in the process of making professional career paths secure. We show that: (i) fixed-term contracts secure professional trajectories if the link between individuals and firms is long enough; (ii) firm networks support the acquisition of skills, making easier professional mobilities; (iii) a "disadvantaged" place of residence seems to be an obstacle in making professional career paths secure.