Immunohistochemical assessment of proliferation marker--Ki67 in nasal polyps tissue and in healthy nasal mucosa was performed. There was no statistical significance difference between percentage of Ki67 positive cells in nasal polyps and nasal mucosa. These cells were observed mainly in epithelial layer and few in subepithelial layer. In examined group Ki67 expression was higher in planoepithelial metaplasia. Assessment of cells proliferation processes could be sensitive and early indicator of neoplasmatic transformation. Examined subgroup in witch Ki67 expression was also higher, was subgroup with eosinophilic infiltrations. Cells proliferation processes in nasal polyps tissue are very important occurrence and require further examinations.