To assess the prevalence and clinical correlates of exercise oscillatory ventilation (EOV) in patients with hypertrophic cardiomyopathy (HCM). Retrospective single-center study. Thirty-six consecutive HCM patients who underwent cardiopulmonary exercise testing. Two patients (5.6%) had EOV. Both patients with peak oxygen consumption (VO ₂ ) less than or equal to 9.1 ml/kg/min had EOV. Left atrial size was greater in patients with EOV. Of the 2 patients in the study population with an abnormal blood pressure response to exercise, 1 had EOV. Both patients with New York Heart Association Class 3 heart failure had EOV. This is the first report of EOV in HCM. EOV is uncommon in patients with HCM. EOV appears to be a marker of disease severity as evidenced by overt heart failure, left atrial enlargement, and low peak VO ₂ .