Investigators at the National Institute of Neurological Disorders and Stroke (NINDS) are seeking individuals with spasmodic dysphonia to participate a study to improve understanding of the disorder's pathophysiology, and to evaluate the role of laryngeal sensation in symptom generation. Eligible participants must be between 18 and 70 years of age, and have spasmodic dysphonia or muscular tension dysphonia. Participants should be without a history of cardiac problems, asthma, or pulmonary disease and should not be currently receiving treatment for their voice disorder. The study will be conducted at the National Institutes of Health (NIH) Clinical Center in Bethesda, MD. All study-related expenses will be paid by the NIH. The study will be carried out under testing and safety standards of the U.S. Department of Health and Human Services. For more information, physicians should send a referral letter and a copy of the patient's recent medical records to Dr. Christy Ludlow, NINDS, NIH, Building 10, Room 5D38, 10 Center Drive MSC 1416, Bethesda, MD 20892-1416; telephone: (301) 496-9366; fax: (301) 480-0803; email firstname.lastname@example.org.