AGN emission above 20 keV: the hard X-ray detection problem.

We have searched the HEAO-4 LED all-sky survey database (13-180 keV) for a class of AGN that is most likely to emit X-rays at energies of ~ 50 keV and above, as a basis for further studies with the Compton Gamma Ray Observatory (CGRO). We have overlayed the survey signals of several samples of AGN-quasars, BL Lacs and Seyfert galaxies - with individual source flux below a significance of 3σ. The objects were selected by their prominence and properties at other wavelengths, and in Einstein observations and the HEAO-A1 survey. We find no significant signal at hard X-rays from any of the chosen classes of radio- loud QSOs and BL Lacs. We find a signal from Seyfert 1 galaxies up to 80 keV compatible with the canonical energy index α=0.7. Keywords: galaxies: active - X-rays: galaxies - γ-ray: observations