Inverted papilloma is a relatively rare benign tumour of nasal mucosa and paranasal sinuses which approx. in 15% is connected with malignancy. The morphology, occurrence, etiology and biological behaviour of this tumour are dealt with. A group of 8 patients is presented. The significance of nasal polyps routine histologic investigation for early detection of these tumours is stressed. Various treatment possibilities are discussed and a therapeutic procedure based on radical surgery is suggested.