Inverted papilloma is an unusual tumour in the nose and nasal sinuses with a marked tendency to recurrence following surgical treatment and with a greatly increased risk for synchronous or metachronous development of carcinoma. A retrospective investigation comprising 42 patients with histological revision revealed an incidence of 0.6/100,000 per annum. Two patients had also carcinomata. No significant differences were observed between the recurrence rates following simple excision, excision via the maxillary sinus or via lateral rhinotomy. Follow-up control for ten years is recommended.