Semiquantitative calculations were made of that portion of the internal friction of annealed and moderately cold‐worked metal single crystals which is due to dislocation motion. The calculations were made on the basis of a qualitative theory of Nowick. It is shown that Nowick's theory leads to reasonable orders of magnitude of the observed internal friction and changes of the modulus of elasticity. At low temperature or at high frequencies (megacycle range) Nowick's hysteresis mechanism becomes inoperative and theories of Koehler and of Eshelby have to be considered to calculate the internal friction.