Fibromyalgia is defined by widespread body pain, tenderness to palpation of tender point areas, and constitutional symptoms. The literature reports headache in about half of fibromyalgia patients. The current epidemiological study was designed to determine the prevalence and characteristics of headache in fibromyalgia patients. Treatment-seeking fibromyalgia patients were evaluated with measures for fibromyalgia, chronic headache, quality of life, and psychological distress. Multivariate analysis of variance (MANOVA) and t-tests were used to identify significant differences, as appropriate. A total of 100 fibromyalgia patients were screened (24 fibromyalgia without headache and 76 fibromyalgia with headache). International Headache Society diagnoses included: migraine alone (n=15 with aura, n=17 without aura), tension-type alone (n=18), combined migraine and tension-type (n=16), post-traumatic (n=4), and probable analgesic overuse headache (n=6). Fibromyalgia tender point scores and counts and most measures of pain severity, sleep disruption, or psychological distress were not significantly different between fibromyalgia patients with and without headache. As expected, the fibromyalgia patients with headache scored higher on the Headache Impact Test (HIT-6) (62.1±0.9 vs 48.3±1.6, p<0.001). HIT-6 scores were >60 in 80% of fibromyalgia plus headache patients, representing severe impact from headache, and 56–58 in 4%, representing substantial impact. In summary, chronic headache was endorsed by 76% of treatment-seeking fibromyalgia patients, with 84% reporting substantial or severe impact from their headaches. Migraine was diagnosed in 63% of fibromyalgia plus headache patients, with probable analgesic overuse headache in only 8%. General measures of pain, pain-related disability, sleep quality, and psychological distress were similar in fibromyalgia patients with and without headache. Therefore, fibromyalgia patients with headache do not appear to represent a significantly different subgroup compared to fibromyalgia patients without headache. The high prevalence and significant impact associated with chronic headache in fibromyalgia patients, however, warrants inclusion of a headache assessment as part of the routine evaluation of fibromyalgia patients.