Muscle-specific creatine kinase (CKMM) plays a vital role in the energy homeostasis of muscle cells. The A/G variation (rs8111989) located in the 3'-untranslated region of the CKM gene has been found to be the most relevant in terms of genetic testing in sport. The aim of the presented study was to test the hypothesis that the G allele might represent a genetic element that contributes to the improvement of endurance performance in Polish and Russian rowers. The distribution of the CKM genotypes was examined in a group of Polish and Russian athletes in comparison with non-athlete controls. There were no statistical differences between the rowers and the control groups across the CKM genotypes when Polish or Russian participants were analyzed. Based on the obtained results, it may be speculated that the CKM A/G polymorphism is not an important determinant of endurance performance level in Polish and Russian rowers. However, these results should be interpreted with caution as they can be limited by many factors.