A self-expanding mount controls transmission of vibration of a vibration source to a base. A main liquid chamber is defined between a resilient member fixed to the vibration source or the base and a casing fixed to the base or the vibration source. A metallic bellows is driven in response to a control signal corresponding to vibration of the vibration source, cause a variation in the pressure of liquid within the main liquid chamber. This variation in the liquid pressure causes contraction and expansion of the resilient member to thereby control the transmission of vibration of the vibration source to the base. A cylinder is formed in the casing and defines part of the main liquid chamber. A driven member is received in the cylinder for axial displacement therein in response to the above control signal. The driven member may be a bellows or a piston.
