 The study design is a phase IV single center, single blind, placebo run-in fixed dose single group study in twenty subjects with moderate to severe restless leg syndrome. It includes a one- three week screening washout period, one week of placebo run-in and four- week treatment period with GEn 600 mg once daily. Subjects will be instructed to take their study medication once daily with food in the evening at approximately 5 PM. If the dose is not taken at the recommended time, the next dose should be taken the following day at the regularly scheduled time about 5 PM the next evening. Subjects will be blinded to treatment placebo versus active drug. 