  The paper describes previous studies of the cosmic X-ray background (CXB) of
the Universe in the energy range 1-100 keV and outline prospects for its
investigation with the help of MVN (Monitor Vsego Neba) experiment. The nature
of the CXB and its use for studying the cosmological evolution of black holes
are briefly discussed. The bulk of the paper is devoted to the methods of CXB
measurements, from the first pioneering rocket and balloon-borne experiments to
the measurements made with latest-generation orbital X-ray observatories.
Particular attention is given to the problems of allowance for the contribution
of background events to the measurements with X-ray and hard X-ray instruments.
