Idiopathic sudden sensorineural hearing loss (ISHL) appears to have man possible etiologic factors. A study of high-resolution computed tomograms on three groups of ears was performed to determine inner ear structure dimensions. Group I, the control group, consisted of 17 ears with no ISHL. Group II, normal site with ISHL, there were 12 ears. Group III, abnormal site with ISHL, was composed of 12 ears. There is little variation in the inner ear dimensions among the three groups. There is also no positive correlation between cochlear aqueduct enlargement and the occurrence of ISHL.