The internal friction of deformed silicon crystals has been measured between 3 and 60 kc/sec, up to 1100°C. The component of internal friction due to dislocations becomes appreciable at 500°C, and rises steadily above this temperature. An Arrhenius plot yields an activation energy of 1.61±0.05 eV for all specimens measured, while the magnitude of the internal friction at any given temperature is approximately proportional to dislocation density and inversely proportional to the frequency. An interpretation of the results is discussed in terms of the kinked‐dislocation theories of Brailsford and of Seeger and Schiller. Suitable augmentation of these theories is shown to bring them into a unified form, which is compatible with the Koehler‐Granato‐Lu¨cke extensible string formulation, at least in the temperature range where thermal kink pair generation is negligible. Reasonable assumptions of kink mobility and density give agreement with the theory; the measured activation energy is then that for kink motion. Comparison with results of Chaudhuriet al.shows that this is less than that for gross dislocation movement.