Lattice dynamics of nearly stoichiometric NbC and TaC phases has beeninvestigated using the Bragg‐intensity measurements at two temperatures (110 and 300 °K). The vibration amplitudes of metal atoms are shown to be smaller compared with those of carbon atoms, the differences decrease with increasing temperature. The separation of the Debye‐Waller factors of both components results in the following values of the Debye temperature: θ300(NbC)(654±6) °K and θ300(TaC)(428±8) °K. Using the common‐amplitude approximation, values of (643±6) and (430±7) °K are found for NbC and TaC, respectively. The results obtained indicate isotropy of the carbide lattices with respect to thermal atomic vibrations over the range 110 to 300 °K.