  The Debye temperature, T_D, of sigma-phase Fe_(100-x)Mo_x compounds with 47 <
x < 56.7 was determined from the temperature dependence of the centre shift of
M\"ossbauer spectra recorded in the temperature range of 80 - 300 K. Its
compositional dependence shows a weak increase with x whose rate, in a linear
approximation, is equal to 3.1 K/at%. The results are compared with the
corresponding ones found previously for the sigma-phase in Fe-Cr and Fe-V
compounds.
