Objective: The objective of this study was to explore the effect of sleep and coping on health-related quality of life in fibromyalgia syndrome (FMS). Methods: Patients diagnosed with FMS (N=101) completed the Positive and Negative Affect Schedule, the Pittsburgh Sleep Quality Index, the COPE, and the Medical Outcomes Study-Short-Form Health Survey for the previous month. Results: Poor sleep quality was reported by 99% of participants. Sleep quality was significantly predictive of pain, fatigue, and social functioning in patients with FMS. Active coping, planning, acceptance, and seeking instrumental and emotional social support were not predictive of health outcomes in FMS. However, the use of restraint coping was predictive of poorer physical functioning. Conclusion: Sleep quality has significant implications for health-related quality of life in FMS. The use of coping strategies contributed little to the models' ability to predict health outcomes in FMS. Interventions designed to improve sleep quality may help to improve health-related quality of life for patients with FMS. (c) 2007 Crown Copyright. Published by Elsevier Inc. All rights reserved.