Hyperventilation syndrome is seldom considered as a diagnostic probability, but nevertheless, it is surprisingly common. By most estimates, this abnormality occurs as the primary or major contributing diagnosis in as many as 10% of all general medical patients1,2 and up to 25% of all patients complaining primarily of “dizziness” or “fainting”3. My experience as a consultant over many years agrees with these estimates. Moreover, several years ago, together with a physician associate, I reviewed the out-patient records of a cohort of applicants referred to us by the U.S.