  Scattering of particles in the gravitational field of rotating black holes is
considered. It is shown that scattering energy of particles in the centre of
mass system can obtain very large values not only for extremal black holes but
also for nonextremal ones. Extraction of energy after the collision is
investigated. It is shown that due to the Penrose process the energy of the
particle escaping the hole at infinity can be large. Contradictions in the
problem of getting high energetic particles escaping the black hole are
resolved.
