The purpose of our study was to correlate the chronological age with Risser staging, knee epiphyseal closure, and bone age by the Tanner and Whitehouse (TW3) or Greulich and Pyle (GP) method simultaneously, to find out the most correlated methods used to calculate the age in a Korean population. A case–control study was carried out in 293 children between the age of 9 and 18 years. Skeletal age was estimated by using the atlas of the GP and TW3 methods; knee epiphysis closure and the Risser staging were also noted. Spearman's correlation coefficient test showed that in both the sexes the GP method is more correlated (r2=0.58 for female patients, range: 0.55–0.61; and 0.58 for male patients, range: 0.54–0.61) with the Risser staging and physeal stages of the knee joint than the TW3 method (r2=0.52 for female patients, range: 0.44–0.61; and 0.55 for male patients, range: 0.48–0.61) in Korean children. Our results suggested that by using the combination of Risser sign, knee epiphyseal closure, and GP bone age, one can calculate a person's chronological age most accurately.