Oral squamous cell carcinoma (OSCC), the most common head and neck cancer, shows poor prognosis as a result of frequent local invasion and lymph node metastasis that is mediated by multiple proteolytic enzymes and angiogenesis. In recent reports, angiogenesis is known to play an important role in tumor invasion and metastasis. The purpose of this study was to determine the role of angiogenesis in OSCCs, particularly with respect to the invasive and the metastatic potential. The microvessel density (CD31) in 34 human OSCC cases were investigated by immunohistochemistry, and reviewed with respect to the invasiveness and the presence of lymph node metastasis and following results were obtained. The blood vessel density (28.8+/-7.9) in the strong invasive cases were significantly higher than those (23.3+/-6.9) in the weak invasive cases. (p < 0.05) In the 14 cases with lymph node metastasis, the average blood vessel density was 28.5+/-9.6. On the other hand, in the 20 cases without lymph node metastasis, the blood vessel density was 25.2+/-6.4. The blood vessel density was not statistically related to lymph node metastasis. (p > 0.05) These results suggest that angiogenesis may be related to the local invasion of OSCC and further research will be needed to investigate the possibility that antiangiogenic agent can be used as an anticancer agent for OSCC.