We present new spectral data of prompt γ-ray emission from the spontaneous fission of 252Cf. This work was performed in direct response to an OECD/NEA high priority data request. We discuss the impact of our new data on evaluated nuclear data tables not only for this nuclide, but also for 238U and 241Pu, which are always produced in a reactor. Furthermore, we will show results from our investigation of prompt γ-ray emission from the reaction 235 U(nth, f), measured in at the Centre for Energy Research of the Hungarian Academy of Sciences in Budapest, Hungary. Spectral data obtained with three different detectors are consistent and led to an uncertainty on total energy and multiplicity considerably smaller than requested by the OECD/NEA.