This chapter discusses nasal polyposis (NP), which is a multifactorial disease which results in edematous masses that obstruct the nasal cavities and paranasal sinuses. Polyps are classified into antrochoanal polyps, isolated large polyps, polyps with chronic rhinosinusitis, polyps with chronic rhinosinusitis, and polyps with specific diseases. The development of a polyp results from chronic inflammation specifically in histological stromal edema with a variable cellular infiltrate. Activation of mast cells, eosinophils, monocytes and macrophages results in arachidonic acid being released from cellular membranes which increases cysLT formation via the 5-lipoxygenase pathway. The surface of the nasal polyps is often covered by the same mucosa that lines the respiratory tract, pseudostratified columnar epithelium. Corticosteroids are the mainstay of medical management of NP, being the only class of medication shown to have proven efficacy in reducing the signs and symptoms.