Objective: To investigate the biologic significance of integrin a5ß1 and avß3 in squamous cell carcinoma of the tongue. Methods: Integrin a5ß1 and avß3 were examined immunohistochemically in 30 cases of squamous cell carcinoma of tongue. Results: The expression of integrin a5ß1 was stronger in well-differentiated squamous cell carcinoma of the tongue than in that of poorly differentiated squamous cell carcinoma. On the other hand, the expression of integrin avß3 was stronger in poorly differentiated squamous cell carcinoma than in that of well-differentiated squamous cell carcinoma. Conclusion: The expression of integrins a5ß1 and avß3 may be related to the differentiation of squamous cell carcinoma of the tongue, and integrin a5ß1 and avß3 within the cancerous tissue may be used for patient prognosis.