Chronic Fatigue Syndrome (CFS) is a prevalent, debilitating, and poorly understood condition that contributes to impaired functioning and increased health care utilization. The vast majority of CFS patients complain of unrelenting sleep disturbances (e.g., sleep onset insomnia and/or sleep maintenance insomnia) that could exacerbate symptoms such as fatigue, mood disturbance, and reduced quality of life. Research with normal sleepers and insomnia sufferers has demonstrated that sleep disruption adversely affects those systems hypothesized to be important in CFS (e.g., neuroendocrine and autonomic systems). Insomnia appears to be a perpetuating factor in CFS, as insomnia appears to develop as a comorbid condition that interacts with and worsens CFS. Perhaps because the insomnia of CFS patients traditionally has been viewed as a secondary symptom rather than as a comorbid disorder, the sleep-specific treatment needs of CFS patients have been largely ignored. In fact, there have been few studies conducted to test sleep-focused therapies with CFS patients. Both our clinical observations and our preliminary studies suggest that those with CFS display sleep targets (i.e., increased time-in-bed, decreased daytime activity) that are common to those with Primary and other comorbid insomnias. These phenomena are known to perpetuate sleep problems, and likely account for the chronic insomnia among CFS patients. Given the high prevalence and cost associated with CFS, as well as its complex clinical picture, interventions that directly address perpetuating mechanisms would likely improve the sleep and general prognosis for these patients.