An engine mount for a vehicle has a first rigid fixture (12) for attachment to the engine and a second rigid fixture (13) for attachment to the chassis or body, an armature (14) attached to the second rigid fixture (13), and a resilient rubber support (10) between the first fixture (12) and the armature (14) for flexing in response to engine vibrations. The rubber support (10) defines a working chamber (22) containing hydraulic fluid which is in communication with a compensation chamber (37) via a helical conduit (38), so that engine vibrations are at least partially damped by oscillation of fluid in the conduit (38) between the two chambers (22,37). Two apertured grills (24,52) define a valve chamber (51) in which a flexible disc valve (46) is oscillatable. The lower grill (52) is rotatable by means of a control rod extending externally of the engine mount. It carries inclined ramps (72) cooperating with similar ramps on a lower plate (55) so that rotation of the lower grill (52) alters the free play of the disc valve (46). In this way, therefore, the flap valve (46) can be controllably rendered operative over a wide range of vibration amplitudes so as (for example) to reduce the dynamic stiffness of the engine mount during engine idling. Other means of adjusting the operation of the flap valve are described.