Therapeutic effects of ibuprofen were evaluated in 46 patients with primary fibromyalgia syndrome in a double blind, placebo controlled study for 3 weeks and in an open trial for another 3 weeks. Several features of primary fibromyalgia syndrome, including number of pain sites, fatigue, swelling feeling, and tender points significantly improved over time in both groups. However, no significant differences were found between the ibuprofen and placebo groups. Improvements in fibromyalgia features might have occurred as a result of physician or study interactions (i.e., an intervention effect). An important observation in our blinded study was that tender point sites among patients with fibromyalgia were significantly (p less than 0.001) consistent at 3 as well as 6 weeks when compared with the baseline.