Case details were reviewed from 2021 patients treated surgically for nasal polyposis between 1991 and 1999, seen by six surgeons serving a catchment population of 805 000. The aim of this study was to determine the incidence of discrepancies between clinical and histological diagnosis. Twenty-two patients (1.1 per cent) were identified as having a lesion that differed histologically from the clinical diagnosis made at the time of surgery and which altered their further management. Amongst them were 11 cases of inverted papilloma, two of Wegener’s granulomatosis, and two of sarcoid. The rest of the cases comprised three of squamous cell carcinoma, one of adenocarcinoma, one of myeloma, one of angiofibroma and one of microcystic papillary adenoma. In this series, the occurrence of malignancy, inverted papilloma, or other clinically significant pathology among the group of patients with otherwise clinically unsuspected histology justifies sending nasal polyps for routine pathologic examination. A cost–benefit analysis showed that, on the basis of 250 cases per year, the cost of laboratory and pathological services would be £12.000, in comparison with the estimated average medicolegal cost of £51.000 per year incurred as a result of a delay in diagnosis together with the pain and suffering which would result given the case mix in this series.