We present investigations on Degenerate Four Wave Mixing in bulk GaAs Fabry-Pérot microcavities at room temperature excited with femtosecond pulses. Due to increased interaction length and amplification of light fields in the cavity, the measured diffraction efficiency η≈2×10−3 at 878 nm is enhanced by a factor of roughly 30 compared to bulk GaAs without cavity. The results may be useful for exploiting the cavity enhancement effect for investigation of carrier kinetics at small excitation densities. For application purposes, the results renew the interest in ultrafast coherent deflectors for all-optical routing.