Measurement of the pressure applied to the anterior region of the palate and incisor region of the mandible during thumb-sucking was carried out 3 female children. A polyethylene bag embedded with a high-sensitivity small pressure sensor was fixed on the ventral side of the thumb so that the baroreceptor could be interposed between the thumb and palate during thumb-sucking. The children were allowed to perform habitual thumb-sucking, and the resulting pressure signals were detected with a high-response dynamic strainmeter and recorded. Measured peak pressures were about 2-4.5kgw, with large individual variation, and waveform patterns also varied. Characteristics of thumbsucking habits and thumb-sucking pressure were related to malocclusion. Measurement of thumb-sucking pressure is believed to be effective for assessment of the qualitative relationship between thumb-sucking and malocclusion.