Healthy normal volunteers and patients with RLS between 18 and 80 years of age may be eligible for this study. All candidates will be screened with a medical history, physical and neurological evaluations, electroymogram (measure of muscle activity), overnight sleep study, electrocardiogram (ECG, measurement of the electrical activity of the heart), and blood and urine tests. They may also have brain or spine magnetic resonance imaging (MRI) or computerized tomography (CT) scans and a chest X-ray. Participants must stop taking all medications prohibited by the study for 2 days or more before the study starts and throughout its duration.