['A number of studies have reported that tumor thickness (the depth of invasion) is a valuable prognostic factor in oral cancers, especially as a predictor of cervical lymph node metastasis. Accurate preoperative assessment of the tumor thickness of tongue cancer would provide useful information for targeting those patients for whom elective treatment of the neck is appropriate when the primary tumor is resected. No studies have been done measuring the tumor thickness of tongue cancer preoperatively. The present study was undertaken in order to evaluate the clinical usefulness of intraoral ultrasonography as a tool to delineate tumor extent and measure the thickness of tongue carcinomas.', 'Twenty-four patients with tongue carcinoma were preoperatively evaluated with intraoral ultrasonography. The tumor thickness measured by ultrasonography was compared with the measurements by histological sections.', 'High-quality ultrasonic images were obtained, and the tumor thicknesses were measurable within 1 mm. There was a significant correlation (P <0.001) between measurements by ultrasonography and histological sections.'] Is intraoral ultrasonography useful to evaluate tumor thickness in tongue carcinoma?