A new kind of force sensor which detects forces by measuring an induced pressure change in a material of large Poisson's ratio was designed and built. In this investigation, mathematical expressions for the sensor's sensitivity and bandwidth were developed. It was shown that the sensor sensitivity can be much larger and its bandwidth is usually smaller than those of existing strain-gage-type sensors. This force sensor is well-suited for measuring large but slowly varying forces. It can be installed in a space smaller than that required by existing sensors. To verify the theoretical derivation, a prototype force sensor was custom designed to fit a linear actuator on the Titan II slave arm designed and built by Schilling Development of Davis, California. This prototype hydrostatic force sensor can measure compressive forces up to 7,200 lbf and tensile forces up to 3,500 lbf.