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Fibromyalgia is a chronic pain disorder, which accompanies chronic widespread pain, vegetative and functional complaints. Etiologic and sustentative factors have not been clearly identified yet. Earlier studies suggested a reduced reactivity of the autonomic nervous system as relevant factor, which was examined by measuring heart rate, heart rate variability, blood pressure and skin conductance levels during physical stress. Another approach focuses on altered muscle tension. Studies concerning this topic have yielded inconsistent results, though. Some studies reported lower muscle tension in fibromyalgia patients in contrast to healthy persons, others didn´t find any difference. Recent studies have investigated the interaction between the cardiovascular system, mediated by baroreflex sensitivity, and pain processing. Fibromyalgia patients showed diminished baroreflex sensitivity compared to healthy controls. Apart from physical, psychic factors, such as stress at work, seem to play an etiopathological role as well. We recorded psychophysiological parameters in 29 fibromyalgia patients and 34 healthy controls during a series of stress and relaxation tasks, in order to investigate the mentioned etiopathological approaches. Mental stress was induced by arithmetic tasks, physical stress by pressure pain on the scapula. We recorded heart rate, blood pressure, heart rate variability, skin conductance level, subjective pain and stress ratings as well as baroreflex sensitivity. Fibromyalgia patients displayed significant higher stress and pain ratings than the healthy persons. But there were no significant differences of EMG values between the two groups. Furthermore fibromyalgia patients displayed significant elevated heart rate and skin conductance levels and diminished heart rate variability. The results indicate an alteration of the autonomic nervous system in terms of elevated sympathetic and diminished parasympathetic tonus. In addition, patients showed significant lower baroreflex sensitivity compared to healthy controls. This could be explained by altered cardiovascular parameters caused by the changes of the autonomic nervous system in fibromyalgia patients. Earlier studies indicate a relation of diminished baroreflex sensitivity and elevated pain perception as well as a possible therapeutic approach consisting of operant conditioning of baroreflex sensitivity.