This research investigates the determinants of international mobility of Ph.D.s upon graduation. It is based on a survey of 400 young Ph.D.s who graduated in France between 2003 and 2008, half of whom were still abroad more than six years after graduating. The impacts of personal, occupational and scientific characteristics on the successive mobility decisions after graduating were scrutinized. The findings show that motivations for going abroad relate principally to the difficulty in finding employment on the French labour market. The choices as to longer term expatriation are more fragmented and can be less readily unravelled. By contrast, readiness to return to France is often accounted for by family factors.