1. As the amount of retained austenite increases (in the limits examined), the damping capacity of the steel increases at all amplitudes of vibration. 2. The increase in the density of defects in the structures facilitates a dissipation of energy only at small amplitudes of unit strain. 3. Isothermal holding at a temperature of 900°C, and especially at 700°, promotes dislocation locking and a decrease in the damping capacity of steel. This effect is maintained up to an aging temperature of 200°C.