Background: The aim of this study was to examine the relationship between age and hamstring flexibility of male soccer players and to provide reference data.Material/Methods: The study comprised 698 male subjects. The largest group consisted of male adolescents (n = 597; aged 10-22 years, yrs), further subdivided into six two-year age groups; the other two groups being children (n = 21, younger than 10 yrs) and adult players (n = 80; older than 22 yrs). All of those who participated in our study were members of competitive soccer clubs. They were examined for anthropometric characteristics, body composition, and performed the sit-and-reach test (SAR).Results: An analysis of variance revealed significant differences between age groups with respect to SAR (F7,690 = 17.62, p<0.001, η2 = 0.15). Our findings indicated that the older the age group, the higher the SAR (e.g. 16.6±5.1 cm in the children's group, 20.7±7.5 cm in the under-16-yr-old group and 24.7±6.9 cm in the adult group). This result came in agreement with the significant and moderate correlation coefficient between age and SAR (r = 0.33, p < 0.001).Conclusions: Although the cross-sectional design did not allow inferring a causal relationship between age and hamstring flexibility, it is reasonable to suppose that there are small gains in flexibility with development. Compared with previous findings, soccer players had similar values to the general population.