  Ultracompact primordial black hole binaries with masses > 10^{16} g are
considered. If PBHB's contribute significant part of the dark matter of the
Galaxy one can expect an existence of high-frequent non-thermal diffuse
gravitational radiation with flux of ~1 erg cm^{-2} s^{-1}. The possibility of
coalescence of the PBHB's in Galaxy's halo to be a source at least of a part of
gamma-ray bursts (GRB) observed is discussed. The energy flux of gravitational
radiation from those GRB's should exceed the energy flux of gamma-radiation by
7-8 orders of magnitude. The possibility of observation of PBHB through
detection of the gravitational radiation burst coincident with GRB is
emphasized. The PBHB also can be observed detecting a stationary gravitatonal
radiation in the frequency range > 10^4 Hz and observing a high-frequent
pulsation of a source's brightness in microlensing effects in the Galaxy's
halo.
