  We study the classical dynamics of a binary stars when there is an
interchange of mass between them. Assuming that one of the star is more massive
than the other, the dynamics of the lighter one is analyzed as a function of
its time depending mass variation. Within our approximations and models for
mass transference, we obtain a general result which establishes that if the
lightest star looses mass, its period increases. If the lightest star win mass,
its period decreases.
