In spite of an intensive campaign to achieve early diagnosis of acoustic neuromas, our attempts have not been successful, since we have even more tumours measuring more than 40 mm in diameter among our latest 100 patients than among the first one hundred. It is demonstrated that both patients and physicians (otologists) are to some extent still ignoring the possible significance of a unilateral, progressive, sensorineural hearing impairment. Guidelines for improving this condition are given. We have been able to follow 21 patients for an average of 4 years, with repeated CT scans, and only in 3 of these patients did the tumour appear to be progressing to a size requiring surgical intervention. In the remaining 18 patients the tumour has not increased in size, as judged by the CT. Because of our complete lack of knowledge about the causes of tumour growth in some patients and absence of growth in others, a more differentiated attitude towards indications for surgery is needed, and in some, mostly elderly, patients a period of 'watchful waiting' is appropriate.