The purpose of the study was to evaluate the efficacy of an extract of Panax ginseng in patients with fibromyalgia. A randomized, double-blind, controlled clinical trial was carried out over 12 weeks to compare the effects of P. ginseng (100 mg/d) with amitriptyline (25 mg/d) and placebo in 38 patients with fibromyalgia: 13 in Group I (amitriptyline), 13 in Group II (placebo), and 12 in Group III (P. ginseng). Ratings on the Visual Analogue Scale (VAS) revealed a reduction in pain in the P. ginseng group (p < .0001), an improvement in fatigue (p < .0001) and an improvement in sleep (p < .001), with respect to baseline characteristics, but there were no differences between the three groups. With respect to anxiety, improvements occurred in the P. ginseng group compared to baseline (p < .0001); however, amitriptyline treatment resulted in significantly greater improvements (p < .05). P. ginseng reduced the number of tender points and improved patients' quality of life (using the Fibromyalgia Impact Questionnaire - FIQ); however, there were no differences between groups. The beneficial effects experienced by patients for all parameters suggest a need for further studies to be performed on the tolerability and efficacy of this phytotherapic as a complementary therapy for fibromyalgia.