The Debye temperature, Θ D, of Fe 100− x Cr x disordered alloys with 0≤ x≤ 99.9 was determined from the temperature dependence of the centre shift of 57 Fe Mössbauer spectra recorded in the temperature range of 60–300 K. Its compositional dependence shows an interesting non-monotonous behaviour. For 0< x≤∼ 45, as well as for∼ 75≤ x≤∼ 95, the Debye temperature is enhanced relative to its value of a metallic iron, and at x≈ 3 there is a local maximum having a relative height of∼ 12% compared to a pure iron. For∼ 45≤ x≤∼ 75 and for x≥∼ 95 the Debye temperature is smaller than the one for the metallic iron, with a local minimum at x≈ 55 at which the relative decrease of Θ D amounts to∼ 12%. The first maximum coincides quite well with that found for the spin-waves stiffness coefficient, D o, while the pretty steep decrease observed for x≥∼ 95, which is indicative of a decoupling of the probe Fe atoms from the underlying chromium matrix, is likely related to the spin-density waves which constitute the magnetic structure of chromium in that interval of composition and show also anomalous dynamic behaviour. The harmonic force constant calculated from the effective Debye temperature of the least Fe-concentrated alloy (x≥ 99.9) amounts to only 23% of the one characteristic of a pure chromium as determined from the heat capacity experiment.