Medically unexplained fatigue occurs in about 5% of the population with 10% of that number fulfilling formal case definitions for chronic fatigue syndrome1. Medically unexplained fatigue is a major problem for both patient and practitioner - for both because there is no effective FDA-approved treatment for the symptom. One major problem for these patients is unrefreshing sleep. Formal sleep studies show reduced total sleep time and reduced sleep efficiency compared to controls.2;3 We are currently in the early stages of an NIH-funded grant designed to study cytokines during sleep. Preliminary results support awake time for patients relative to controls, producing a decreased sleep efficiency. These data lead to our working hypothesis that the problem of severe daytime fatigue is due to a previously unappreciated form of sleep pathology related to sleep fragmentation.