The purpose of this prospective, controlled study was to estimate the prevalence of immune-mediated (autoimmune) inner ear disease in a high-risk patient population, in order to determine the predictive value of a positive lymphocyte transformation test. The high-risk group was defined as any dizzy patient with unilateral or bilateral-asymmetric sensorineural hearing loss, who had not previously received immunotherapy. From more than 400 consecutive patients with a chief complaint of dizziness, 58 were entered into the study over an 8-month period. The control group consisted of 15 normal volunteers. Thirteen patients (22%) one control (7%) had positive lymphocyte transformation tests. The data suggest that positive results in "high-risk" patients are more common than previously believed. Assuming test sensitivity is 96%, specificity 93%, and disease prevalence 22% in high-risk patients, the predictive value of a positive lymphocyte transformation test using inner ear membranes is 79%. That is, approximately three fourths of all positive results are true positives. Positive results in suspected patients, therefore, should be considered true positives, and treatment recommended. Future research should attempt to refine the putative antigen(s), further define "high risk" patients, and prospectively verify these preliminary results.