On the basis of a comparative analysis of the Hungarian uprising of 1956 and the Mexican mobilization of 1968, this paper examines the relationship between the notions of student movements and political generations by asking whether the latter are formed a posteriori by reference to a collective action in the past or whether, on the contrary, they exist a priori, thus constituting one of the subjective foundations of the mobilized group. An analysis of the Hungarian and Mexican cases will allow us to show that we can grasp the links between the two ideas not in terms of causality but in terms of interactions.