The study of the intermediary states or physiological determinants of a liability to emotional behaviour at adolescence necessarily calls forth the psychology of development and endocrinology of behaviours. If one holds on to hormon biology, and sex hormons in particular, both levels of significant effects may be summed up in an activating influence, contemporary to puberty and a far prior organizing influence, contemporary to the ante- and peri-natal period. According to both these levels of influence, one should be able to distinguish between the direct and indirect effects, knowing that all of them are at work simultaneously, in proportions that are of course diverse and often very difficult to precise. The data we have at present suggest that we should relativize a far too simplistic image of a » hormonal storm » wherefrom an emotional » storm and stress » specific to adolescence would result. These data stress important differences according to the sex and also stress the joint part played by the several factors coming from the environment.