To investigate the expression of mammary serine proteinase inhibitor(Maspin) in patients with oral squamous cell carcinoma and its relationship with clinicopathological features. The Maspin protein expression was examined in 45 patients with oral squamous cell carcinoma and in non-malignant oral epithelia by immunohistochemical staining. The relationship between the Maspin protein expression and the clinicopathological parameters was statistically analyzed. The Maspin protein expression in the cancerous tissues of oral squamous cell carcinoma was lower than that in the non-malignant oral epithelia (P = 0.001). Negative correlation was found between the Maspin protein expression in cancerous tissue and the status of lymph node metastasis (P = 0.038). Positive Maspin protein expression indicated negative lymph node metastasis, and negative correlation was also found between the Maspin protein expression and the postoperative metastasis (P = 0.004). Positive correlation was found between the Maspin expression and the patients' survival rate (P = 0.014), patients with positive Maspin protein expression having higher survival rate than those with negative Maspin expression. Maspin might be useful as a potential prognostic marker for oral squamous cell carcinoma.