Abstract. The effect of disruptive selection for body conformation on body weight and length, tail length, and femur weight and length at different stages of development (21, 42, 63, and 120 days of age) was analysed in four mouse lines of the CBi stock selected for (CBi+, CBi-) and against (CBi/L, CBi/C) the phenotypic correlation between body weight and tail length, and die unselected control line CBi. As expected, body weight and tail length distributed according to the selection criteria; rrunk length (whole body length minus tail length) behaved as body welght at all ages. CBi/L had the highest femoral length (p < 0.01), and CBi/C attained the highest femoral weight (p < 0.01). CBi+ and CBi-, harmonically large or small, differed between them and from the control line in both variables (p < 0.001). These findings further corroborate the proposal that bone mass is markedly affected by the skeleton function as support of soft tissues. The allometric analysis ofthe regression of femur weight on femur length suggests that, in this model, a) the demand posed by the selective pressure forced each genotype to find a unique Solution, b) this response is sex-dependent, and c) genetic determination ofthe parameters involved in this allometric relationship is, at least, partially independent.