  We present the study of two 3-brane system embedded in a 5-dimensional
space-time in which the fifth dimension is compactified on a $S^{1}/Z_{2}$
orbifold. Assuming isotropic, homogeneous, and static branes, it can be shown
that the dynamics of one brane is dominated by the other one when the metric
coefficients have a particular form. We study the resulting cosmologies when
one brane is dominated by a given single-fluid component.
