It is demonstrated that, under certain conditions, the spectrum of a monochromatic xray beam analysed by a multicrystal spectrometer includes several spurious peaks. These erroneous peaks are the result of the angular separation of dynamically and kinematically diffracted radiation. The above separation of the diffracted radiation occurs when the diffraction takes place near, instead of on, a reciprocal lattice point, at one of the spectrometer's crystals.