 We will direct a clinical trial of Whole Body Hyperthermia WBH for the treatment Fibromyalgia. Although we have not yet studied WBH for Fibromyalgia we have data indicating that WBH is effective for the acute treatment of major depression MDD. Given the high overlap of symptoms between Fibromyalgia and Major Depressive Disorder MDD, we have reasons for expecting that WBH may also be of benefit for Fibromyalgia. The primary objective of the proposed study is to determine if WBH produces improvement in core Fibromyalgia symptoms, just as it appears to do in MDD. Indeed, in preliminary studies, a single exposure to WBH resulted in a downward shift in body temperature Figure 6 and a decrease in depressive symptoms as measured using the Center for Epidemiologic Studies Depression Scale known as the ADS in Germany where this study was conducted 5 days later Figure 7. In addition, following exclusion of one patient with bronchopulmonary inflammation that did not show a decrease in body temperature following treatment, a correlation between the shift in body temperature and ΔADS approached statistical significance Figure 9. These preliminary data are consistent with previous studies showing that 1 patients with seasonal affective disorder in winter during depression have blunted thermoregulatory cooling but have thermoregulatory cooling that is similar in efficiency to control subjects after successful antidepressant response to phototherapy the retina has direct projections to DRVL serotonergic neurons, 2 ECT increases the circadian amplitude of core body temperature, and decreases mean core body temperature, particularly during the nighttime thermoregulatory cooling period, and 3 thermoregulatory cooling, as evidenced by the number of active sweat glands in depressed patients, increases upon clinical recovery, but not earlier, following ECT. We hypothesize that these relationships in preliminary data and in previous studies are due to dysfunction of the afferent signaling arm of the thermoregulatory system in MDD, specifically the warm afferent system projecting to the LPB and, secondarily, to the DRVLVLPAG and DRI subsets of serotonergic neurons that have been implicated in anxiolytic and antidepressant actions, respectively, and to normalization of warm afferent signaling following treatment. Again given the high degree of overlap between Fibromyalgia and MDD, we expect that WBH may confer therapeutic benefits in Fibromyalgia as it appears to do in MDD. 