Abstract: A method is provided for directly measuring the contact pressure on the mating interfaces of two solids undergoing compression where the interfacial region contains an entrapped film of liquid. An acoustic pulse is directed at either interface. A reference amplitude of the acoustic pulse reflected from the interface is measured as it bears initial contact pressure. A second "loaded" amplitude of the acoustic pulse reflected from the interface is measured when the interface is bearing a different contact pressure. A measure indicative of the change in contact pressure is computed from the ratio of the reference and loaded amplitude measurements by correlation with a calibration curve.