Recent studies have provided some clues with regard to the relationship existing between uncoupling proteins (UCPs) and blood pressure in animal experiments. In an attempt to determine the genetic polymorphisms of UCPs that are associated with blood pressure in humans, we have analyzed genetic polymorphisms in members of the UCP family, including UCP1, UCP2 and UCP3. Methods : In this study, we assessed the association between UCP genotypes and systolic blood pressure (SBP) and diastolic blood pressure (DBP), in a population comprised of 832 Korean female subjects, using a general linear model, which was adjusted for both age and BMI. Results : Among 14 SNPs and the haplotypes constructed from them, haplotype3 of UCP1 (UCP1-ht3) evidenced significant associations with SBP (P=0.0053) and DBP (P=0.0130). However, this haplotype was not significantly associated with obesity phenotypes, including BMI or fat mass (P>0.05), thereby suggesting that its association with blood pressure was not mediated by obesity phenotypes. Conclusions : The source of variations in SBP were determined to occur in the following order: BMI (12.8 %), age (1.2 %) and UCP1-ht3 (1.1 %). Although BMI appears to exert greater effects on blood pressure, the UCP1-ht3 genotype was also found to exert a significant effect.