Changes in the relative weights of carcase, abdominal fat, breast and leg muscles, and plasma thyroid hormone concentrations occurring during the first 6 weeks of postnatal growth were analysed in Japanese quail males divergently selected for high and low relative body weight (BW) gain between 11 and 28 d of age, respectively, and constant adult BW. The results suggest that the selection for the shape of the growth curve, like the selection for body fat, modifies the carcase quality owing to shortening/prolongation of the acceleration growth phase. Individuals with a short acceleration phase of the growth curve are characterised by low carcase quality during the fattening period.