The aim of this study was to determine the prognostic value of Ki-67 immunostaining in laryngeal squamous cell carcinomas. Ki-67 labeling was quantified in 63 laryngeal squamous cell carcinomas by counting at least 1,000 tumor cells in the most immunoreactive area in each sample, and the Ki-67 labeling index was calculated as a percentage. The antigen expression was compared with clinical factors, histopathological grading and prognosis. The Ki-67 mean proliferation index for all patients was 25.44% ( range, 2-75%). A significant correlation was found between Ki-67 mean proliferation index and patient age (P<0.05), T-stage (P<0.05), nodal metastasis (P=0.001) and recurrence (P<0.001). There was no significant association between the Ki-67 mean proliferation index and tumor site or histologic grade. A univariate analysis showed that the Ki-67 labeling index >21% (P<0.001), T-stage (P<0.001) and nodal metastasis (P=0.001) are determinants of recurrence. In the multivariate analysis, the Ki-67 labeling index >21% (P<0.001), T-stage (P<0.001) and nodal metastasis (P<0.05) were independent predictors of recurrence. Kaplan-Meier plots of survival in patients with Ki-67 values above and below the median (21%) of the general study population showed that a high Ki-67 labeling index correlated with a shorter disease-free survival (P<0.0001). The analysis of the Ki-67 labeling index at the time of initial surgery may be a powerful prognostic marker for patients with laryngeal squamous cell carcinoma and may be useful for selecting subgroups of patients who should be treated with more aggressive therapies.