OBJECTIVE A cyclin-dependent kinase inhibitor, p27kip1, is recognized as a negative regulator of the cell cycle. To clarify whether immunohistochemical detection of p27 might provide prognostic information, we investigated the expression of p27 in laryngeal squamous cell carcinoma (SCC). STUDY DESIGN A retrospective study of patients was performed in 109 cases of laryngeal SCC. In addition, we investigated the expression of p53 and granulocyte colony-stimulating factor receptor (GCSF-R) to examine the prognostic significance of them in the same samples. METHODS Immunohistochemical staining by specific monoclonal antibodies was performed using the avidin-biotin-peroxidase complex technique. RESULTS Advanced tumor size and clinical stage and the occurrence of lymph node metastasis were associated with the absence of p27 expression, but not correlated with p53 expression and GCSF-R expression. The overall 5-year survival rate in the p27-positive group was significantly higher than that in the p27-negative group. In the Cox proportional hazard model, p27 was demonstrated to be the most powerful prognostic factor among gender, tumor size, lymph node metastasis, stage of disease, and p53 and GCSF-R expression. CONCLUSIONS We concluded that assessment of p27 expression is useful as a prognostic factor for laryngeal SCC and of value in selecting patients with laryngeal SCC for aggressive therapy.