This study was carried out to examine the effect of short-term selection for 5-weeks of age body weight in divergent lines of Japanese quail. Growth curves for both sexes within each selection group resembled the general sigmoid shape of a typical growth curve. Gompertz model curves and the observed growth curves were very similar. In both males and females the parameter estimates of the Gompertz growth curve were obtained with a high determination coefficient (0.9898 > R2 > 0.9840). Sex differences in asymptotic weight were found to be significant across lines. Similarly, in both sexes a significant divergent selection effect was determined for parameter A. The growth rate in all the Japanese quail lines was significantly higher in males than in females. There was also a significant increase in growth rate of the females selected for increased 5-week body weight over the control females, as well as a significant decline in growth rate of males selected for decreased 5-week body weight compared to the unselected control group.