Although the human genome has now been sequenced, the influence of gen polymorphisms on gentic predisposition to sports is largely unknown. Numerous studies were conducted concerning the determination of association of the alpha-actinin-3 gene (ACTN3) polymorphism with performance of elite athletes. ACTN3 gene codes alpha-actinin-3, which is found only in fast, type II muscle fibers. C-to-T transition (rs.1815739 C/T) in exon 16 of the ACTN3 gene leads to a stop-codon (R577X polymorphism), which results in a-actinin-3 deficiency in XX homozygotes (no alpha-actinin-3 protein detectable in muscle fibers). Functional ACTN3 R577X polymorphism has been associated with athletic performance. In the present study, the authors was performed to determine the quality and the quantity of DNA extracted from buccal swabs and to estimate PCR products. The amplified fragment subsequently underwent digestion by DdeI to determine ACTN3 R577X genotype and allelic frequencies of 88 Vietnamese athletes belong to young and national teams. The authors obtained genotype and allelic frequencies of ACTN3 R577X from 54 running athletes (44 percent RR
43 percent RX
13 percent XX and 66 percent R, 34 percent X) and from 34 swimming athletes (29 percent RR
53 percent RX
18 percentXX and 56 percent R, 44 percent X). Together with physical characteristics and the obtained performance, these results are used in order to analyze and evaluate the effect of ACTN3 gene on the performance of Vietnamese athletes. Further, the target is focusing to study gen technology on selecting athletes, that aims to reduce costs of athlete selection, coaching, and enhance Vietnamese athletes's performance.