Tumor thickness (the depth of invasion) is a valuable prognostic factor in oral cancers, especially as a predictor of cervical lymph node metastasis. The aim of our thesis was to assist in proper diagnosis for tongue cancer by measuring tumor thickness using intraoral ultrasonography preoperative. All patients examined their neck nodes preoperative by sonar, asking can we determine nodal metastasis depending on tumor thickness detected for every case. Our results supported by postoperative pathology.10 patients suffered for deep pain and inability to swallow or eat examined in our tests. The case who gave us positive readings for nodal metastasis by sonar preoperative was for a patient suffers from tongue lesion 9mm.Many reports and thesis indicated that nodal metastasis by tongue cancer happened when tongue lesion thickness was more than 3mm or 4 mm. Another reports and articles said that to have nodal metastasis, tumor thickness should exceed 5 mm. No articles could determine what is the actual tumor thickness cause nodal metastasis. Our thesis by results could determine that when lesion exceeded 5mm in thickness precisely at 9mm, nodal metastasis founded.This can help and assist in clinics for oral and maxilla facial surgeries that when we found tumor lesion affected tongue and measure its thickness by intraoral sonar giving 5mm or more, the incidence of metastasis to neck lymph nodes is high.