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Forty healthy youth, 20 aged Chinese volunteers and 400 dizzy patients were tested with SHAT at frequencies of 0.01-0.64Hz. The peak velocity was 50 degrees/s. The commonly used three parameters: phase, gain, asymmetry were calculated by computer. Alertness tests in the darkness demonstrated a gain increase and a decrease of phase lead with increasing frequency. The bilateral responses were symmetrical in normal volunteers. The asymmetry value was in the limit of 5 degrees. The values of all the parameters made no sexual difference. The phase value with 0.01Hz in the aged volunteers was a little smaller than that in the younger volunteers. An abnormal result was found in 204 patients (51%). Phase lag decreases were the most common abnormal results. Both patients with Meniere's disease and with central disorders revealed phase lag decreases. However, patients with central lesions showed decreases of phase lag in more frequencies. Direction of asymmetry in patients with central lesion was in good correlation with the side of lesions. The five common types of abnormality were reported in the present paper, they were vestibular habituation and asymmetry, vestibular habituation, vestibular asymmetry in higher frequencies, vestibular deficit and vestibular hyperreactivity.