  The effective perturbation theory developed by Braaten and Pisarski for gauge
theories at finite temperature is extended to finite chemical potential. As a
first application the collisional energy loss of a heavy quark propagating
through a quark-gluon plasma with non-vanishing quark chemical potential is
considered. Assuming $\mu /T\simeq 1$, motivated by numerical simulations of
heavy ion collisions at RHIC energies, we find that the effect of the quark
chemical potential is rather small, unless the energy density instead of the
temperature is fixed.
