The medical evaluation of patients with complaints of dizziness and disequilibrium often includes a quantitative assessment of their vestibular function. Clinically approved tests for assessing the horizontal semicircular canals currently exis (caloric testing, rotational chair testing) and a new test, crHIT, has the advantage of significanty improving resul0ts of patient evaluation compared to existing tests. However, for assessing the vertical, i.e., the anterior and posterior semicircular canals, there are currently no established tests. The Computerized Rotational Head Impulse Test-Vertical (crHIT-vertical) has the potential to reliably assess the vertical semicircular canals and have a major impact on the management of patients with dizziness and disequilibrium. The goal of this Phase I SBIR proposal is to develop the additional hardware, analysis software, and clinical protocol necessary to adapt a commercially available clinical rotational test system, i.e., the Neuro Kinetics, Inc. (NKI) I-Portal(r) Neuro-Otologic Test Center (NOTC) for performing this new test and validating results on a limited number of subjects and vestibular patients. The long-term aim of this project is to verify the clinical efficiency of crHIT-vertical and sell this test to identify and characterize th severity of an asymmetry of vestibular function. The immediate goals of this Phase I SBIR are described by the two Specific Aims of this application. The first aim is to develop a clinical version of the crHIT-vertical: integrate all of the necessary components of hardware and software into the existing commercial rotational test system manufactured by Neuro Kinetics, (head restraint, calibration procedure for six degrees of freedom head sensor, stimulus delivery, data acquisition, and data analysis). The second aim will verify implementation of the crHIT-vertical stimulus delivery and VOR analysis software on the NKI NOTC system on 20 subjects with normal vestibular function and 20 subjects with a verified vestibular loss of vertical canals function. The tests will be performed in a clinical vestibular laboratory and will provide feedback that will be used to evaluate test comfort and to improve the user interface to the analysis software. The results from the clinical tests will be used to optimize the crHIT- vertical in advance of a Phase II SBIR test protocol.