Cyclin D1 is a cell cycle regulator essential for G1 phase progression and a candidate protooncogene implicated in the pathogenesis of several human tumor types, including head and neck carcinomas. And pRb acts as tumor suppressor and its function seems to be regulated by CDK(cyclin-dependent kinase)-cyclin complex. So immunohistochemical staining with monoclonal antibody against cyclin D1 protein(BioGenex G124-326) and pRb(NCL-Rb) was done to investigate clinicopathologic meanings of cyclin D1 protein and the relationship between cyclin D1 protein and pRb in head and neck squamous cell carcinomas. The results were as follows : 1) The positive rate of cyclin D1 was 25%(10/40) in head and neck squamous cell carcinomas. There was no significant difference in the positive rates of cyclin D1 protein among subsites of head and neck regions. 2) The positive rates of cyclin D1 were not affected by clinicopathologic parameters in head and neck squamous cell carcinomas. 3) The positive rates of cyclin D1 were affected by positivity of Rb protein in head and neck squamous cell carcinoma. In conclusion, cyclin D1 protein can be a oncogenic potential but may not affect the clinicopathologic outcomes in head and neck squamous cell carcinomas. And the expression of pRb may stimulate the expression of cyclin D1 protein.