OBJECTIVE To assess the frequency and characteristics of benign paroxysmal positional vertigo (BPPV) and clinical test of sensory interaction and balance (CTSIB) abnormalities in patients with ankylosing spondylitis (AS). STUDY DESIGN A series of consecutive patients that fulfilled the modified New York diagnostic criteria for AS and matched controls were studied. SETTING The study was performed at the Otolaryngology Division of a tertiary reference center. PATIENTS Fifty-nine patients with AS (47 men [79.6%]) attending hospital outpatient rheumatology clinics between March and October 2008, and 46 controls (34 men [73.9%]) were studied. INTERVENTION Dix-Hallpike and cephalic rotational tests and CTSIB were performed in AS patients and age-, sex-, and ethnically frequency-matched controls. MAIN OUTCOME MEASURE Type and frequency of BPPV and CTSIB conditions were assessed. RESULTS BPPV was diagnosed in 6 patients (10.1%) with AS and in 2 (4.3%) of the controls (p = 0.24). Abnormal caloric test was more commonly observed in patients with AS (n = 15 [25.4%]) than the controls (n = 0) (p < 0.001). Increased frequency of abnormal CTSIB also was observed in patients (19/59 [32%]) compared with the controls (3 [6.5%]) (odds ratio, 6.81 [95% confidence interval, 1.77-38.0]; p = 0.001). Among the abnormal CTSIB patterns, the vestibular loss was the most commonly observed in patients with AS (15/59 [25.4%]). CONCLUSION The present study shows an increased frequency of abnormal postural control in CTSIB test of vestibular origin in patients with AS.