Chronic fatigue and nonrestorative sleep are prominent features of fibromyalgia (FM). It has been reported that these patients have alpha-wave intrusion during nonrapid eye movement (NREM) sleep (stages 2,3,4). Although alpha-NREM sleep has been noted in patients with other rheumatic disorders, a paucity of controlled data limits the interpretation of these reports. To determine the specificity of alphaNREM sleep, FM patients were compared with pain-free controls and with patients with generalized musculoskeletal pain without evidence of FM. There were no statistically significant differences in alpha-NREM percentages among the three groups. However, nearly half of all "pain" subjects (FM and generalized pain controls) had alpha-NREM percentages above the maximum value found in the painfree control group, and the mean percentage of alpha-NREM approached significance when pain-free controls were compared with all pain patients (FM plus generalized pain controls). These results provide additional evidence that alpha-NREM sleep may be a more generalized marker for chronic pain rather than a specific anomaly in patients with FM. Therefore, at present, sleep studies, although possibly of value in identifying factors associated with FM, should not be used in an attempt to either confirm or exclude a diagnosis ofFM in patients with generalized nonarticular pain.