A study to compare the therapeutic efficacy of aerobic exercise and paroxetine in fibromyalgia syndrome. The aim of this study is to compare the therapeutic efficacy of aerobic exercises versus paroxetine in a randomized, controlled study. Sixty female patients between ages 18-50, diagnosed as fibromyalgia syndrome by the 1990 American College of Rheumatology criteria were randomly allocated to one of three groups. Group I was given aerobic exercises on bicycle ergometer for 40 minutes, 3 times a week for 6 weeks, group II was given paroxetine 20 mg daily for 6 weeks and group III was given placebo Transcutaneous Electrical Nerve Stimulation for 20 minutes, 3 times a week for 6 weeks as a control group. All groups were evaluated at admission, termination and at the end of 6 months by Visual Analog Scale (VAS), pressure algometric testing, weekly analgesic consumption for pain intensity. They were also evaluated for psychological and social status, Beck Depression Inventory. Statistical analysis was done by the SPSS (Statistical Package for Social Sciences) program with T-test, Oneway-Anova, Mann-Whitney U, Wilcoxon Rank Sum Test and post-hoc. Pain threshold with pressure algometer, pain intensity by VAS and BDI scores showed significant decrease compared to scores of the group III at termination of the study and at 6 months follow-up while base-line evaluation parameters demonstrate no significant statistical differences between groups. Analgesic consumption was reduced only in group I. As a result this study shows that paroxetine and aerobic exercises have better therapeutic effect when compared to placebo group on short and long-term follow-up with no significant difference on evaluation parameters in two groups.