  The radial component of the motion of compact binary systems composed of
neutron stars and/or black holes on eccentric orbit is integrated. We consider
all type of perturbations that emerge up to second post-Newtonian order. These
perturbations are either of relativistic origin or are related to the spin,
mass quadrupole and magnetic dipole moments of the binary components. We derive
a generalized Kepler equation and investigate its domain of validity, in which
it properly describes the radial motion.
