The prevalence of fibromyalgia (FM) in males is much lower than in women. Thus, current knowledge about the syndrome has been developed from research with women. The aim of the present study is to analyze whether FM manifestations differ as a function of sex. Two clinical groups with FM (21 males and 21 women) and a control group of healthy men (n= 21) participated in the study. Several aspects of pain, sleep, fatigue, psychopathology, emotional distress and functional impact of FM were evaluated with an algometer and questionnaires. The clinical groups showed a significantly greater impairment than the control group in all the self-report measures. However, the FM patients only showed significant differences in the sensibility threshold to the pain, which was lower in the women. In addition, the best predictor of the experience of pain in males was sleep quality, and in the women, catastrofying pain. Our results suggest that the most effective therapeutic strategies to control pain may be different for men and women.