Nasopharyngeal malignancy accounts for less than 2 per cent of all head and neck cancers. Serous otitis media (SOM) causing deafness is a recognized indicator of nasopharyngeal obstruction and the possibility of a nasopharyngeal malignancy must be considered in all adults. Examination under anaesthesia (EUA) and biopsy of the nasopharynx is routinely undertaken in many centres to rule out nasopharyngeal malignancy in adults with SOM. The purpose of this 10-year retrospective study was to evaluate the case records of all adult cases of SOM, including their presentation, clinical findings, management and nasopharyngeal biopsy results. Eighty-five patients were included in the study. Fifty-nine presented with unilateral SOM and 26 with bilateral SOM. The primary presenting complaint in all cases was hearing loss. A nasopharyngeal mass was documented in 55 patients (69 per cent). Four nasopharyngeal masses were noted to have irregular or exophytic mucosa on flexible nasendoscopy. All patients underwent a EUA of the ears and a nasopharyngeal biopsy. The four patients with suspicious-looking masses were all found to have malignancies (two squamous cell carcinomas, one B-cell non-Hodgkin lymphoma and one adenocarcinoma). Three of these patients presented with unilateral SOM and one with bilateral SOM. All other patients with masses were found to have benign lymphoid hyperplasia. In total, 4.7 per cent of the adults with conductive hearing loss secondary to SOM were found to have a malignancy on nasopharyngeal biopsy. We would advocate a high index of suspicion of a nasopharyngeal tumour in adults presenting with SOM. If a mass is found in the nasopharynx then it should be biopsied. If no mass is found then it is not necessary to biopsy; however, close follow up, with repeat fibre-optic nasendoscopy, is advised.