We administered a standardized history questionnaire and performed a tender point examination on 27 patients with debilitating fatigue of at least 6 months duration, seen in a primary care practice, as well as on 20 patients with fibromyalgia. Sixteen of the 27 patients with chronic fatigue met the full criteria for the working case definition of chronic fatigue syndrome (CFS). Eight patients with chronic fatigue denied having any current persistent, diffuse musculoskeletal pain, and their tender point scores were similar to those in 10 normal control subjects. In contrast, 19 patients with chronic fatigue (70%) had persistent, diffuse musculoskeletal pain. The results of their tender point examinations were similar to those of the patients with fibromyalgia. Thus, the majority of these patients with debilitating chronic fatigue, including those who met criteria for CFS, met the historical and tender point diagnostic criteria for fibromyalgia. The presence of current musculoskeletal pain will identify those CFS patients who have fibromyalgia.