  We describe light-like boosts of the Kerr gravitational field transverse and
parallel to the symmetry axis. In the transverse case the boosted field is that
of an impulsive gravitational wave having a line singularity displaced relative
to its position if the rotation of the source were removed. The parallel boost
is insensitive to the rotation of the source. The literature contains a number
of diverse results for light-like boosts of the Kerr gravitational field. Our
conclusions confirm the correctness of the limits calculated by Balasin and
Nachbagauer [Class.and Quantum Grav.13(1996),731]. To avoid any ambiguity our
approach is centered on evaluating the light-like boost of the Riemann tensor
for the Kerr space-time with the metric playing a secondary role.
