Caffeine is known to increase neural excitability in the brain by blocking adenosine receptors through the central nervous system in the body. Xanthine is the main component of caffeine (1,3,7-trimethylxanthin) and reaches high plasma concentrations in the circulation within about 1 hour after consumption, but this time can vary from person to person. Caffeine also inhibits the use of carbohydrates by promoting the use of free fatty acids as fuel, which delays the depletion of muscle glycogen and increases the body's ability to burn fat. The rate of caffeine metabolism varies between individuals depending on genetic variation. Caffeine is metabolized by the CYP1A2 gene, which encodes the cytochrome P450 (CYP) enzyme, an enzyme from the oxidoreductase class. It has been reported that some polymorphisms in the CYP1A2 gene have an effect on caffeine metabolism. CYP1A2 is significantly synthesized in the liver and enzyme activity may differ in individuals. This difference is due to genetic and non- genetic factors (such as smoking, race, gender, diet, disease, drug use). The presence of the rs2069514 (-3860G> A) polymorphism of the CYP1A2 gene is associated with a lower rate of expression of the gene and has been found to metabolize caffeine more slowly. The rs762551 (-163C> A) polymorphism on the same gene is associated with high enzyme activity. Depending on the body's ability to metabolize caffeine, the stimulating effect of caffeine will also change. Caffeine consumed in the same amount has a stronger stimulating effect on slow metabolism than fast metabolism. Caffeine helps improve performance and is beneficial for athletes to speed up their reaction time and increase their endurance during long exercise periods. The aim of this study is to analyze the distribution of polymorphisms in rugby players by analyzing the rs2069514 and rs762551 polymorphisms of CYP1A2, which may affect sports performance. 12 rugby players participated in our study. DNA isolation from blood samples collected by signing consent forms; it was completed using the Invitrogen (Van Allen Way Carlsbad, CA, USA) commercial kit. For ACTN3 genotyping, real-time polymerase chain reaction (Real-Time PCR) protocol was performed. In the CYP1A2 rs2069514 polymorphism, 11 out of 12 rugby players (92%) were determined to be GG and 1 GA (8%) genotype. No AA genotype was found in our study. When allele distributions were examined, it was observed that the G Allele was 96% and the A Allele was 4%. In CYP1A2 rs762551 polymorphism, it was determined that 1 (8%) of 12 rugby players was CC genotype, 9 (75%) CA and 2 AA (17%) genotype. When allele distributions were examined, it was observed that the C Allele was 46% and the A Allele was 54%. CYP1A2 enzyme activity associated with performance enhancing effects in athletes may vary from person to person. In our research group, according to the results of our study in CYP1A2 rs762551, 2 athletes with AA genotype may experience faster caffeine metabolite accumulation. A total of 10 athletes from AC and CC genotypes may experience slower caffeine metabolite accumulation. According to the results of our study in CYP1A2 rs2069514, 11 athletes with GG genotype reported that the caffeine metabolite accumulation pattern was normal. It has been reported that only one athlete with GA genotype has a slow caffeine metabolite accumulation pattern. This study is the first to examine the relationship between the CYP1A2 gene and caffeine in rugby players. Thus, our study will contribute to the genetic information pool and support other studies in this field.