Recently, hydraulic mounts have begun to supplant conventional all-rubber mounts in an effort to reduce the transmission of engine vibrations to the vehicle frame. To date, hydraulic mount technology has been largely restricted to passive implementation. This paper presents a lumped parameter dynamic model of an adaptable hydraulic mount, and introduces two semi-active property control schemes for the mount. Variations of over 100% have been demonstrated for the key mount properties of stiffness and damping. Experimental results of stiffness and damping rates are presented and compared to model predictions. A sensitivity analysis relating the effect of parameter variations to mount properties is also presented.