Résumé : Objectives: The objective of this study was to evaluate the efficacy and safety of pirlindole [75 mg b.i.d.], a reversible and selective inhibitor of monoamine oxidase A [RIMA] in the treatment of primary fibromyalgia syndrome [FMS]. Methods: One hundred patients were included in a four-week double- blind placebo-controlled study. The safety analysis was based on 89 patients [45 pirlindole and 44 placebo] and the efficacy analysis on 61 patients [33 pirlindole and 28 placebo]. The evaluation of the outcome of therapy was based on the results obtained on eight characteristic parameters [pain, morning stiffness, tender pain score, psychological evaluation using the Symptom Checklist-90-Revised, fatigue, sleep disturbance, global evaluation by the patient, global evaluation by the investigator]. Results: When compared with baseline evaluation a significant improvement [P < 0.05] was noticed for all the parameters with pirlindole whereas three parameters only [tender point score, psychological score, global evaluation by the patient; P < 0.05] were significantly improved by the placebo. Moreover, at the end of the four-week treatment period, pirlindole appeared to be significantly superior to placebo on four parameters [pain, tender point score, global evaluation by the patient and the investigator]. Side-effects were observed in 40% of the pirlindole-treated patients and 36.4% of the placebo-treated patients leading to 13.3% and 6.8% drop-outs, respectively. These differences were not statistically significant [P > 0.05]. Conclusion: This four-week double-blind placebo-controlled trial suggests that pirlindole [75 mg b.i.d.] might be a well-tolerated and beneficial treatment for FMS patients.