Out of 100 students following their curriculum in the same university, 10 are mobile. Between the 2nd and 3rd cycle, that ratio reaches 30%. This study shows the advantages of better knowing the inter-university migrations in an increasingly competitve context. It underlines that in Ile-de-France, the growth of vocational training was profitable, since in outer suburb universities, the relative contribution from students beginning a 3rd cycle and coming from another university is higher than in central universities. This work underscores the role of disciplinary specialization and the polycentric structure of interuniversity migrations in the metropolitan regional space.