In this study fibromyalgia sufferers were randomly administered a combination of monoamine-oxidase inhibitors (MAOIs)-A/B with 5-HTP, 5-HTP alone, MAOIs-A/B alone, or the tricyclic drug amitriptyline in order to compare the efficacy of these treatments. The benefits on the painful syndrome were assessed by using Visual Analogic Scale score rating from 0 to 4. The combination of MAOIs with 5-HTP significantly improved fibromyalgia syndrome as determined by Visual Analogic Scale whereas the other treatments yielded poorer benefits. No subject withdrew from the trial due to adverse effects, even if some sleep disturbances and mild stomach-ache were reported. The tolerability of the association MAOIs/5-HTP was good, although a transient cheese effect occurred in one of the patients treated with MAOIs as well as in a patient treated with the association MAOIs and 5-HTP. No one of these two cases was due to pharmacological dietetic mistake of the patient. In both the cases the transient hypertension was associated to very dramatic emotional events. The benefits obtained by using the combination of MAOIs with 5-HTP can be explained with a treatment-induced enhancement of aminergic and serotonergic transmission. The recently shown high prevalence of migraine in the population of fibromyalgia sufferers, suggests a common ground shared by fibromyalgia and migraine. Migraine has been demonstrated to be characterized by a defect in the serotonergic and adrenergic systems. A parallel dramatic failure of serotonergic systems and a defect of adrenergic transmission have been evidenced to affect fibromyalgia sufferers too. Enhancing serotonergic analgesia while increasing adrenergically mediated analgesia seems to be an important tool in fibromyalgia. Treatment consisting with the association MAOIs/5-HTP is aimed at enhancing serotonergic/adrenergic transmission by inducing an up-regulation of serotonergic/adrenergic receptors and a simultaneous increase of serotonin levels in the central nervous system.