Scattering of particles in the gravitational field of rotating black
holes is considered. Expressions for scattering energy of particles in
the centre of mass system are obtained. 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. It is shown that for realizing of the collisions with infinite
energy one needs the infinite interval not only of the coordinate time
but also the infinite interval of the proper time of the free falling
particle.