Fibromyalgia (FM) is a rheumatologic disorder of unknown etiology affecting predominantly women. Recent studies demonstrate that FM is characterized by abnormalities in pain regulation. Considerable human and animal researach indicates that reproductive hormones influence processing of painful stimuli; however, the effects of hormonal activity on on pain processing in FM remains unknown. Therefore, the proposed research examines whether fluctuations in gonadal hormones across the menstrual cycle affect clinical symptomatology and experimental pain responses in FM patients and matched controls. All subjects will complete daily ratings of pain and other clinical symptoms for two complete mentrual cycles. Also, experimental pain resonses will be assessed during the follicular and luteal phases of the menstrual cycle in all participants. It is hypothesized that FM patients will report substantially greater clinical symptomatology, inlcuding increased pain, sleep disturbance, fatigue and mood disturbance, during the luteal (i.e. prementrual) compared to the follicular (i.e. post-menstrual) phase, while cycle phase will produce minimal impact on clinical symptoms among controls. In addition, it is hypothesized that both FM patients and controls will exhibit greater sensitivity to experimentally-induced pain during the luteal versus the follicular phase, and this enhanced pain response during the luteal phase will be more robust among FM patients. The present study represents a one-year pilot project to begin investigating the role of hormonal factors in FM. We plan to utilize these pilot data to assist in the development and submission of an NIH appalication proposing a more extensive multi-year study of this issue. It is anticipated that the results of the study will allow us to refine our model of the etiopathogenesis of abnormal pain perception in FM with respect to the interactions between sex hormones and the peripheral and central nervous system pathways that may be involved in altered pain perception and abnormal functional brain activity.