Two-hundred and fifty years after Valsalva's discovery that fixation of the stapes could be a cause of deafness, there is still a lack of knowledge about the etiology and pathogenesis of otosclerosis. The purpose of this study was to obtain more information about the natural history of this disease by correlating the volumes and activity of otosclerotic lesions within the temporal bone to the patient's age and sex. Fifty temporal bones from 33 patients (19 females and 14 males) with otosclerotic lesions were reviewed microscopically. The degrees of activity of these foci were assessed and, using a computer based technique known as "digitizing", the volumes of each otosclerotic lesion were calculated. The results of this study indicate that there is no statistical difference in volumes between males and females. From the results obtained, it is suggested that there appear to be two growth patterns of the otosclerotic lesion: one pattern grows for a very short period and then becomes dormant or inactive. The other type of otosclerosis shows a continuing growth and progression throughout life.