The measurement of tooling-workpiece interface loads is needed for process monitoring, analysis and design. One approach to measuring local interface loads with minimal disturbance of the surface and process is to embed sensors in the surface below the surface region of interest. Small piezoelectric sensing elements were cast into polymer surfaces and their ability to measure loads applied normal to the surfaces was assessed. Sensor outputs were characterized in terms of sensor depth below the surface, the distance along the surfaces from the load location to the sensor location and sensor to sensor spacing. A mechanical model of the sensor-surface system was developed which predicted sensor output.