Several investigators have suggested that there is a strong correlation between tumor depth and lymph node involvement in tongue carcinoma. The purpose of this study was to investigate the relationship between the shape of tumor, tumor depth, and lymph node metastasis in tongue carcinoma. Fifty-four patients with T1 abd T2 tongue carcinomas who underwent surgical treatment were included in this study. Tumors were divided into four categories according to their shape of invasion: superficial, exophytic, endophytic, and a combination of endophytic and exophytic. Forty cases of endophytic and combination types were divided into two groups according to the shape of invasion: (1) reductive bottom of invasion (n = 17) and (2) expansive bottom of invasion (n = 23). Tumors with a reductive bottom of invasion showed a variety of tumor depths and had low lymph node involvement (4/17, 23.5%). However, tumors with an expansive bottom of invasion showed deeper invasion and a high incidence of lymph node metastasis (16/23, 69.6%). These results suggested that the macroscopic shape of invasion is a feature that may provide important information about the prognosis of the primary tumor especially in relation to cervical lymph node involvement.