Fibromyalgia syndrome (FS) is a rheumatic syndrome affecting to 2-3% of individuals of productive age, mainly women. Neuroendocrine and genetic factors may play a significant role in development of the disease which is characterized by diffuse chronic pain and presence of tender points. Several studies have suggested an association between FS, especially pain sensitivity, and polymorphism of the catechol-O-methyltransferase (COMT) gene. The aim of the present study was to characterize the SNPs rs4680 and rs4818 of the COMT gene and assess its influence in pain sensitivity of patients with fibromyalgia screened by the Fibromyalgia Impact Questionnaire (FIQ). DNA was extracted from peripheral blood of 112 patients with fibromyalgia and 110 healthy individuals and was used as template in PCR for amplification of a 185-bp fragment of the COMT gene. The amplified fragment was sequenced for analyses of the SNPs rs4680 and rs4818. The frequency of mutant genotype AA of SNP rs6860 was 77.67% in patients with FS and 28.18% for the control group. For the SNP rs4818, the frequency of mutant genotype CC was 73.21 and 39.09% for patients with FS and controls, respectively. Moreover, the FIQ score was higher in patients with the homozygous mutant genotype for SNPs rs4680 (87.92 points) and rs4818 (86.14 points). These results suggest that SNPs rs4680 and rs4818 of the COMT gene may be associated with fibromyalgia and pain sensitivity in FS Brazilian patients.