The present study is an examination of the effects of quality and quantity of social support on the psychological and physical well-being of women with fibromyalgia syndrome (FMS). Participants were 568 women who were members of a health maintenance organization (HMO) with a confirmed diagnosis of FMS. Participants were administered a battery of questionnaires assessing their psychological and physical well-being. Measures of depression, self-efficacy, helplessness, mood disturbance, health status, impact of FMS, and social support were included. Regression analyses indicated that larger social support networks were associated with greater levels of self-efficacy for pain and symptom management, while the perceived quality of social support was associated with lower levels of depression, helplessness, mood disturbance, impact of FMS, higher levels of self-efficacy for function and symptom management, as well as overall psychological well-being. These findings indicate that the quality of social support is more important than quantity in determining outcomes in women with FMS. Thus, the quality of social support has important financial and psychosocial implications for the individual and for the community as a whole. Future research should examine longitudinal changes in quality of social support and the corresponding changes in health status and psychological well-being, as well as the effects of integrating manipulations designed to affect the quality of social support into community interventions designed to enhance the well-being of women with FMS. (Contains 2 tables.)