The frequency of nasal polyp in a population of outpatients in an allergic clinic is found to be about 4%, while it is 2% in the rhinitis group in the field of otolaryngology. Allergy and infections are generally accepted as important etiological factors in the formation of nasal polyps. The aim of this study is to find out the morphologic findings, the distribution of mast cells, and immunoglobulin E(IgE) in the nasal polyps. The results were as follows : 1) The surface epithelium of nasal polyps was mainly lined by pseudostratified ciliated columnar epithelia. 2) Mast cells were present throughout the stromal tissue and especially around blood vessels. 3) IgE was aggregated predominantly in the stromal tissue.