Objectives: To evaluate the clinical significance of cyclin-dependent kinase 1 (CDK 1 ) in 77 oral squamous cell carcinomas (OSCC) using immunohistochemical methods. Study Design: Immunohistochemical expression of CDK 1 was compared with various clinicopathological features in 77 OSCC and 60 controlled epithelia adjacent to the tumours. In addition, correlation of CDK 1 expression and prognostic and the 5-year accumulative survival rate of OSCC were investigated. Results: The CDK 1 protein was expressed in 52 cases of 77 tumor tissues (67.5%), compared with 21 cases of 60 controlled (35.0%). The expression of CDK 1 was significantly correlated with the histological grade of OSCC ( P <0.05). The CDK 1 protein was over-expressed in recurrent tumors or in those with lymph node metastasis. Statistical analysis showed a significant reduction in the 5-year accumulative survival rate in CDK 1 positive cases compared with CDK 1 negative cases ( P <0.05). Namely, the CDK 1 positive patients had poor prognosis. Conclusions: The expression of CDK 1 might serve as malignant degree and prognostic markers for the survival of OSCC