 Fibromyalgia as a clinical syndrome is defined by chronic widespread muscular pain, fatigue and tenderness with hyperalgesia to pressure over tender points. Pain associated with fibromyalgia can interfere with daily function, work, and social activities. Thus, one of the main treatments for patients with fibromyalgia must focus on pain relief to allow the person to function more independently both at home and at work. Although the etiology of fibromyalgia is unknown, there is clearly enhanced sensitization in the central nervous system pain pathways as demonstrating by decreases in pressure pain thresholds, reduced central inhibition, and enhanced temporal summation. Reducing pain in people with fibromyalgia would help increase the patients ability to return to work, perform activities of daily living and thus improve the quality of life for the patient. Transcutaneous electrical nerve stimulation TENS is a modality utilized in physical therapy that delivers electrical stimulation through the skin and is used for both acute and chronic pain. TENS works by reducing central excitability and increasing central inhibition. Thus, the investigators hypothesize that application of Transcutaneous Electrical Nerve Stimulation TENS to patients with Fibromyalgia FM will reduce pain, reduce central excitability by restoring diffuse noxious inhibitory controls DNIC, and reduce temporal summation and that this decrease in pain andor central excitability will improve function. The primary aim of the study is to test the effectiveness of TENS on pain and central excitability in a crossover design study for patients with Fibromyalgia with random assignment to three treatments: no treatment control, placebo TENS and active high frequency TENS. A secondary aim is to test the effect of decreased pain and central excitability on function in patients with Fibromyalgia. 