Throughout a selection experiment, which extended over five generations: the base and four generations of selection for augmenting early growth rate (GR) during the period from hatch to 21 days of age in Japanese quail, a total number of 8724 birds were used: 1726 in the base population, 5176 for the selected line (HGR_1-21) and 1822 for the control line. The most important results obtained as follows: Genetically, heritability (h²) for all body weights (BW) showed moderate h² ranged from 0.19 to 0.29. The GR_1-21 positively correlated with all body weights weekly measured except BW at hatch (BW₁₎ with genetic correlations (r_g) ranged from 0.06 to 0.47, and a wide range of phenotypic correlation (r_{p < /sub>) ranged from 0.18 to 0.52. The  GR during  different periods of growth had medium  h² ranged from 0.17 to 0.28 and showed a wide range of moderate to high rg with the selection criterion (0.15 to 0.70) and had a broader range of rp < /sub> ranged from 0.03 to 0.67. The HGR1-21 line in the 4^th generation had the best growth performance for each of BW7, BW21, BW28, GR during the periods 1-7, 1-14, 1-28 and 1-35 days of age with significant differences. The realized cumulative  response after four generations of selection was 0.063 (6.30%) for GR1-21, the cumulative correlated responses for BW s and GR s ranged from 1.19,g to 23.94,g and from 3.10% to 17.00%, respectively. So, the current study aimed to evaluate the effectiveness of the selection program through estimation of direct and correlated responses to selection for fast GR1-21, and determination of correlations between selection criterion and either body weights at different ages or GRs during different growth periods for Japanese quail.}