  We show how to include a chemical potential \mu in perfect lattice actions.
It turns out that the standard procedure of multiplying the quark fields \Psi,
\bar\Psi at Euclidean time t by \exp(\pm \mu t), respectively, is perfect. As
an example, the case of free fermions with chemical potential is worked out
explicitly. Even after truncation, cut-off effects in the pressure and the
baryon density are small. Using a (quasi-)perfect action, numerical QCD
simulations for non-zero chemical potential become more powerful, because
coarse lattices are sufficient for extracting continuum physics.
