Forty-four patiants who had squamous cell carcinoma of the tongue, that could examine into the primary lesion and cervical lymph node, were studied. The evaluation of histopathological malignancy in the primary lesion of squamous cell carcinoma of the tongue was discussed, together with how this was related to cervical lymph node metastasis. It has been confirmed that carcinoma invades into the deep layers, carcinoma might become less differentiated.Histological variables examined included invasion within the muscle layer, length of muscle layer, depth of invasion within the muscle layer, perineural and lymphovascular space invasion, histological differentiation (the whole, the part of invasive front, the change in deep layer).A statistial association with cervical lymph node metastasis was found in the following factors: the depth of invasion within the muscle layer (p<.01), perineural invasion (p<.01), and grade of histological differentiation in the most invasive lesions (p<.05). It has further been shown that there is a close relationship between perineural invasion and the depth of muscle layer invasion. This suggests that perineural invasion is one factor that enhances the increase in depth of invasion within the muscle layer.Our treatment policy for the above is that if carcinoma is not metastasis into cervical lymph node and the invasion of the muscle layer is less than 7mm in the primary lesion, we will resect the primary lesion only and then carry out a histopathological study to determine the prognosis.