We studied tenderness at 75 unilateral anatomic locations in 10 fibromyalgia patients and 10 normal control subjects to determine which sites best identified patients with fibromyalgia. Using a dolorimeter, the mean amount of pressure required to elicit tenderness was significantly lower in patients than in controls at 19 sites (P less than 0.001). Of the previously proposed tender points, only 2 were included in those 19 best discriminating points. Fifteen of the 19 best discriminating points were clustered in regions around the anterior shoulder, anterior chest, posterior scapula, and medial knee. The 19 sites that we have identified best separate patients with fibromyalgia from controls, although the discriminating power of these sites in other chronic pain syndromes will require further study. Examination of specific regions may be more useful clinically than the exact anatomic sites within these regions.