For the past 25 years, the 'alpha-delta NREM sleep abnormality' has been used by some as a defining or legitimizing marker for poorly defined rheumatic diseases such as fibromyalgia and chronic fatigue syndrome. Comprehensive review of the literature reveals no support for such a conclusion. Most studies involve small numbers of patients. The lack of control subjects, non-standardized recording techniques, and confusion between tonic and phasic alpha frequency activity patterns make comparison difficult. There is much evidence that this sleep EEG pattern is not only non-specific, but may actually reflect a sleep maintaining process. The 'sleep fragmentation' theory of the complaint of non-restorative sleep in this patient population is invalidated by the fact that conditions characterized by severe sleep fragmentation, such as obstructive sleep apnea, are not associated with musculoskeletal symtoms. It is difficult to attribute musculoskeletal symptoms to disorders of sleep in view of the fact that the only organ of the body known to benefit from sleep, or to be adversely affected by lack of sleep, is the brain. It is concluded that fibromyalgia and chronic fatigue syndrome are associated with subjective sleep complaints, but do not represent sleep disorders.