Seven cases of inverted papilloma with malignant change, of the nasal cavity and paranasal sinuses, were referred to the department of radiotherapy in Newcastle between 1979 and 1990. All patients received postoperative radiotherapy, which, in three, prevented further recurrence; in the remaining four, locally recurrent disease proved resistant to both radiotherapy and chemotherapy, ultimately becoming fatal. Only one of seven patients developed cervical lymph node metastases. Postoperative radiotherapy is of value in about 40% of patients. It is most useful when only microscopic residual disease is seen. Radiotherapy and chemotherapy, when used for bulky macroscopic disease, were of no value.