  The role of the relativistic amplitudes for a number of ${\cal O}(k)$
processes usually neglected in potential model calculations of
NN--bremsstrahlung is investigated. In particular, we consider the
$\Delta$--excitation pole contributions related to the one--pion and one--rho
exchange and in addition include the exchange contributions induced by the
radiative $\omega,\,\rho \to \pi \gamma$ decays. The contributions are
calculated from relativistic Born amplitudes fitted to $\Delta$--production and
absorption data in the energy range up to 1 GeV and then used to supplement
potential model and soft photon calculations for nucleon--nucleon
bremsstrahlung. The effects on $NN\gamma$--observables, although moderate in
general, are found to be important in some kinematic domains.
