A study was conducted to determine BW, feed intake, feed efficiency, and carcass composition changes following 51 generations of selection for high 4-wk BW in Japanese quail. Quail lines utilized were the P line selected for high 4-wk BW on a normal 28% CP diet and the unselected base population (C line) from which the P line originated. Body weight, feed intake, and feed efficiency data were collected daily from 1 to 28 days, whereas percentage carcass water, ash, protein, and total lipid data were obtained at 0, 4, 7, 10, 14, 21, 28, 42, and 56 days of age. Body weights of P line quail were significantly (P < .05) larger than BW of C line quail at all ages with the greatest deviation occurring at the age of selection. Feed intake was significantly greater in the P line and paralleled BW increases. When feed intake was adjusted for differences in BW, P line quail consumed less feed per gram of BW than C line quail and adjusted feed intake declined with age after Week 1. The P line quail had superior feed efficiency compared with C line quail from 1 to 13 days of age with the greatest deviation immediately posthatch. Carcass composition determinations revealed significant (P < .05) age and line effects. Both percentage ash and protein increased from hatch to 14 days and thereafter remained constant. However, percentage water and total lipid demonstrated contrasting responses to increasing age; percentage water declined whereas percentage total lipid increased. The P line quail had less carcass water and protein, but had more lipid.(ABSTRACT TRUNCATED AT 250 WORDS)