Nasal polyposis is a chronic inflammatory disease of the nasal and paranasal sinuses mucosa, characterized by prolapse of edematous mucosa, most commonly from the area of anterior ethmoid. The mean histological characteristics are proliferation of pseudostratified respiratory epithelium, thickening of the basement membrane, focal fibrosis and eosinophilic and lymphocytic infiltration of the lamina propria. Although etiology is unknown, two hypotheses are dominant among the scientists: "hypothesis of staphylococcal superantigens" and "hypothesis of immune barrier dysfunction". Although we have not yet achieved a full understanding of the precise mechanisms underlying the pathogenesis of this disease, it is known that nasal polyposis is associated with intensive chronic inflammation, followed by dysregulation of chemotaxis, migration, activation and function of eosinophils. A great number of cytokines, chemokines, and adhesion molecules are involved in the regulation of these complex mechanisms. After activation, eosinophils produce and release enzymes, which can lead to the damage of mucosa and tissue remodeling. Hyperactive eosinophils release a new amount of chemokines and cytokines, attracting new eosinophils into the site of inflammation, and may cause the persistence of chronic inflammation.