Some features of recent results in renormalization theory

These lecture notes are devoted to a review of some results obtained in perturbative renormMization theory during the last years. The most powerful technique developed during that period consists in the formulation of quantum action principles: these theorems, firstly derived in the BPHZ framework, hold independently of the renormMization method to be used. Moreover, they contain the basic information given by renormalization theory, namely the