In spite of many recent advances in basic science, the etiology and pathogenesis of nasal and paranasal polyps have still not been clarified. Well defined causal factors are hereditary diseases such as cystic fibrosis and primary ciliary dyskinesia. Allergic and non-allergic processes of the airways, particularly intrinsic asthma and intolerance to non-steroidal antiinflammatory drugs (NSAID), are implicated in the development of nasal polyposis. Histopathological studies of polyp tissue do not allow etiologic or prognostic conclusions, but are indispensable for the classification of structures involving clinical signs similar to nasal polyps. Causal antiallergic therapy is confined to the rare cases with an evident clinically relevant nasal allergy. Topical corticosteroids are effective in the treatment of nasal polyposis, but in extensive and obstructive polyps surgery is required. In severe polyposis of the ethmoid sinus endoscopically controlled endonasal ethmoidectomy is the surgical treatment of choice.