Records of 1,530 Japanese quail were used to estimate heritabilities and genetic correlations based on a derivative-free restricted maximum likelihood (REML) method with an animal model and ANOVA. The animal model included fixed effects of hatch and sex, random effects of additive genetic value of the bird, and common environmental effect of the dam. Heritabilities estimated from REML for body weights at hatch, 7, 14, 21, and 28 d of age were .38, .12, .31, .12, and .44, respectively. Heritabilities estimates from the sire component of variance for the same traits were .57, .08, .28, .15, and .47. These values indicate that genetic progress can be made by selecting for either 14-d or 28-d body weight. Genetic correlation (REML) of .76 between body weights at 14 and 28 d of age indicates the possibility of improving body weight at 28 d of age by selecting for body weight at 14 d of age.