Far‐infrared transmission measurements have been made on pure and Fe2+‐doped MnF2at 4.2°K using magnetic fields up to 105 kOe. By means of Fourier‐transform spectroscopy we have investigated the behavior of the spin‐wave modes near the spin‐flop transition. Both the AFMR and the two‐magnon absorption with theEfield perpendicular to thecaxis have been measured. In Fe2+‐doped MnF2the spin flop occurs at higher fields depending on the Fe2+‐concentration. The localized mode which splits linearly in low fields no longer shows a linear dependence in the spin‐flop region.