[en] In this paper, the authors review the gamma-ray data on the active galactic nuclei observed to date and we draw some conclusions as to their general characteristics. A number of possible gamma-ray production mechanisms are discussed in light of these measurements. In particular, the relevance to gamma-ray emission of jet structures is presented. The active galaxies contribution to the cosmic diffuse background at gamma-ray energies is estimated. Future prospects for extragalactic gamma-ray astronomy are outlined in view of the coming generation of gamma-ray telescopes