Abstract: A process for making piezo-electric polyvinylidene fluoride (PVDF) film for use, for example, as diaphragms for telephone transmitters, includes the steps of: (a) stretching the melt-extruded film parallel to the extrusion direction with a stretch ratio of about 4 to 1 at about 120.degree. C. to convert it to a .beta. crystalline form; (b) clamping the film between conductive rubber pads to which the polarizing voltage, e.g. 1.3 kv for 12 .mu.m film is applied. While the voltage is thus applied, the film is heated to about 110.degree. C. for 130 mins. and cooled to ambient with the polarizing filed preset; (c) conductive elastomer electrodes are applied to the film in the desired pattern; and (d) the piezo-electric properties are stabilized by heating the foil to about 90.degree. C. for 2 hours.