Background: Patients with fibromyalgia report persistent widespread pain, fatigue, and substantial functional limitations, which may lead to high health resource use (HRU) and lost productivity. Previous analyses of the U.S. population have not examined the direct and indirect costs of fibromyalgia by severity level., Objectives: To assess (a) HRU, direct and indirect costs associated with fibromyalgia in routine clinical practice in the United States using a patient-centric approach, and (b) the relationship of fibromyalgia severity level to HRU and costs., Methods: This study recruited a nonprobability convenience sample of 203 subjects aged 18 through 65 years between August 2008 and February 2009 from 20 U.S. community-based physician offices. Subjects had a prior diagnosis of fibromyalgia by a rheumatologist, neurologist, or pain specialist; received treatment at the enrolling physician's practice for at least 3 months; experienced widespread pain for at least 3 months; and experienced pain in the previous 24 hours. Subjects completed a 106-item patient questionnaire that included 5 validated health-related quality-of-life instruments and study-specific questions about demographics; clinical history; overall health; treatment satisfaction; and impact of fibromyalgia on cognitive function, daily activities, and employment status. Subjects also self-reported hours of unpaid informal caregiver time because of inability to perform daily activities (e.g., housework, child care), out-of-pocket expenses for medical and nonmedical services, and lost productivity related to fibromyalgia for the previous 4 weeks. The 20-item Fibromyalgia Impact Questionnaire total score was used to stratify subjects into fibromyalgia severity groups (0 to less than 39 = mild, 39 to less than 59 = moderate, 59 to 100 = severe). Staff at each site recorded clinical characteristics, HRU, and medication use attributable to fibromyalgia on a paper clinical case report form (CRF) based on a 3-month retrospective medical chart review. Unit costs for 2009 were assigned to the 3-month HRU data reported on the CRF and 4-week subject-reported lost productivity. Costs were then annualized and reported in the following categories: direct medical, direct nonmedical, and indirect. Differences across severity levels were evaluated using the Kruskal-Wallis test (continuous measures) and Pearson chi-square or Fisher's exact tests (categorical measures) at the 0.05 alpha level., Results: Of the 203 subjects, 21 (10.3%) had mild, 49 (24.1%) had moderate, and 133 (65.5%) had severe fibromyalgia. For subjects with mild, moderate, and severe fibromyalgia, respectively, the number of fibromyalgia-related medications (3-month means: 1.8, 2.3, and 2.8, P = 0.011) and office visits to health care providers (3-month means: 2.7, 5.2, and 6.9, P < 0.001) significantly differed across severity levels. Across severity levels, total medical and nonmedical out-of-pocket costs also differed (P = 0.025). Mean [median] 3-month total direct costs (including payer costs for HRU and out-of-pocket costs for medical and nonmedical services) were $1,213 [$1,150], $1,415 [$1,215], and $2,329 [$1,760] for subjects with mild, moderate, and severe fibromyalgia, respectively (P = 0.002); and mean [median] 3-month indirect costs (including subject-reported absenteeism, unemployment, disability, and the estimated value of unpaid informal care) were $1,341 [$0], $5,139 [$1,680], and $8,285 [$7,030] (P < 0.001). Mean total indirect costs accounted for 52.5%, 78.4%, and 78.1% of mean total costs for subjects with mild, moderate, and severe fibromyalgia, respectively., Conclusions: Direct and indirect costs related to fibromyalgia are higher among subjects with worse fibromyalgia severity. Indirect costs account for a majority of fibromyalgia-related costs at all fibromyalgia severity levels.