Fibromyalgia is characterized by diffuse musculoskeletal pain and fatigue. There are limited data about systemic steroid treatment of patients with fibromyalgia in the English literature. Patients with fibromyalgia with ongoing diffuse musculoskeletal pain despite standard treatment, extreme fatigue and elevated C-reactive protein (CRP) levels without evidence of synovitis, or other source of inflammation, were asked to participate in our study. After consent, demographic, clinical and laboratory parameters in addition to body mass index were documented. These patients were interviewed and asked to answer the Revised Fibromyalgia Impact Questionnaire (FIQR) just prior, 1 and 4 weeks following 14 mg depot betamethasone intramuscular injection. Twenty-three patients were recruited and 21 completed the study. 19 patients were women with mean age of 42±10.12 and CRP level of 14.1±3.96 mg%, and all had negative rheumatoid factor and antinuclear antibodies. All patients had significant improvement in all of the FIQR parameters, at 1 and 4 weeks, except memory, anxiety and balance. It can be concluded that systemic intramuscular depot betamethasone injection seems to have a favorable effect in patients with fibromyalgia with elevated CRP levels for at least 4 weeks.