An intraoral ultrasonographic technique was developed using a small transducer which can be easily inserted into the oral cavity. The commercially available Toshiba SAL-35A ultrasonic image processor was used in these evaluations with three different configurations of transducers, each equipped with a small ultrasonic conductor to eliminate air between the transducer face and the region to be surveyed. This apparatus allows ultrasound observation of any area in the oral cavity. Thirty-five patients with oral neoplasms were examined to ascertain the efficacy of this technique. They were classified histologically as 21 cases of squamous cell carcinoma, 7 cases of pleomorphic adenoma, 3 ameloblastomas, 3 hemangiomas and 1 acinic cell tumor. Ultrasonographic findings of the tumors were evaluated with respect to the shape, as regular or irregular; the border, as smooth or rough; and the internal echo, as weak, strong or heterogeneous. The ultrasonographic findings revealed that all squamous cell carcinomas exhibited irregular shapes, and nineteen of the twenty-one had rough borders. 4 cases exhibited strong internal echoes, 9 cases exhibited weak internal echoes and 8 cases showed heterogeneous internal echoes. All cases of pleomorphic adenoma exhibited regular shapes and smooth borders. Three of seven exhibited weak internal echoes, and 4 cases showed heterogeneous internal echoes. All cases of ameloblastoma and hemangioma showed irregular shapes and homogeneous internal echoes. Comparing the ultrasonographic and histological findings, ultrasonography revealed additional details of the histological structure of the tumors. It is concluded that intraoral ultrasonography is useful in the diagnosis and treatment of oral neoplasms.