Chronic fatigue syndrome is a disabling illness for which there is no specific treatment. As a group, CFS patients have disturbed sleep with frequent arousals and the sense of not having slept upon awakening. Xyrem (Sodium oxybate) is known to improve deep sleep and so may reduce the sleep disturbances of CFS leading to better sleep with less fatigue. Its ability to produce the rapid onset of deep sleep is a reason it became a street drug, but its availability is currently limited via distribution through a single centralized pharmacy. Xyrem has been successfully used based on results from a study on patients with fibromyalgia (FM), an ailment closely resembling CFS. However, in that study, the researchers provided no information as to whether patients had FM alone or FM plus CFS. Thus, it is not clear from this study just which patient may be helped. I have prescribed Xyrem for patients who have both FM and CFS with good results. In this study, funded by the company that makes Xyrem, I propose testing the drug's efficacy on patients with CFS alone - that is, they do not have fibromyalgia.