Several studies have shown that the thickness of tongue carcinoma is related to prognosis and to the likelihood of cervical node metastases. We investigated whether preoperative estimates of tumor thickness and volume, as determined from magnetic resonance imaging (MRI), correlated with histologic thickness and might therefore predict the presence of neck metastases. We assessed relationships between histologic tumor thickness and MRI tumor thickness and volume in a retrospective series of 33 patients with squamous cell carcinoma of the tongue. Thicknesses were determined by direct measurement and by considering corrections for ulceration or tumor vegetation (reconstructed thickness). Relationships between MRI thickness and the presence or absence of homolateral and contralateral nodal metastases were also investigated. We found that MRI thicknesses correlated strongly and directly with histologic tumor thicknesses, although mean MRI thicknesses were significantly greater than histologic thicknesses. MRI thicknesses were significantly greater in patients with contralateral neck involvement than in those with no neck involvement. We conclude that MRI provides an accurate and reproducible means of estimating the thickness of tongue carcinomas, paving the way for further studies on more extensive series of patients to determine whether preoperatively determined MRI thickness can reliably predict homolateral and bilateral neck involvement.