Despite new technology, diagnosis of the dizzy patient remains a problem. While computer analysis permits objective, quantitative assessment of vestibular function, the large variability in normal subjects makes diagnosis difficult-particularly in minor dysfunction. This study assesses the diagnostic capabilities of the three modalities of vestibular testing: caloric irrigation, sinusoidal rotation, and posturography. METHODS AND MATERIALSSeventy consecutive patients with subjective reports of vertigo underwent extensive vestibular evaluation. The group included 23 men and 47 women, with an average age of 46.7 years. Final diagnosis was based on clinical impressions and interpretation of diagnostic tests.Bithermal caloric stimulation was performed using the Fitzgerald-Hallpike technique, with responses considered to be abnormal when asymmetry exceeded 20 percent. Rotational testing included multiple frequency sinusoidal rotations in the dark about a vertical axis. Methods of stimulation, eye movement recordings, and data analysis have been published previously. ' Posturographic testing was performed using the commercially available computerized dynamic posturography platform. A complete description of this test is available in the literature.' Results of the tests were compared to normative data collected in the laboratory or supplied by the manufacturer in the case of posturography. RESULTSIn this group of patients, diagnoses included: endolymphatic hydrops ( 12); acoustic neuroma (6); unilateral peripheral dysfunction (1 5); bilateral peripheral dysfunction (5); nonlocalizing vestibular dysfunction