Abstract: Associations between the C/T polymorphism of the UCP2 gene (AlaVal55, rs660339) and aerobic and anaerobic components of physical fitness of athletes were studied. The study involved 168 athletes (46 women and 122 men) engaged in various sports and 98 nonathletes (35 women and 63 men). The athletic performance testing program included the ramp test on a treadmill and the Wingate anaerobic test on a bicycle ergometer. The group of athletes exhibited a tendency towards a higher frequency of carriers of two alleles of “mitochondrial efficiency” (UCP2*TT) (χ2 = 2.53, p = 0.28). Val55 allele associations (T*UCP2) with higher values of functional indicators characterizing the aerobic abilities of athletes were demonstrated, whereas athletes carrying two original Ala55 alleles (UCP2*CC) had better anaerobic abilities. © 2018, Pleiades Publishing, Inc.