  We extend previous calculations of polarization observables for the
annihilation reaction $\bar p +p\to \ell^{-}+\ell^{+}$ to the case of heavy
leptons, such as the $\tau$-lepton. We consider the case when the beam and/or
the target are polarized, as well as the polarization of the outgoing leptons.
We give the dependence of the unpolarized cross section, angular asymmetry, and
various polarization observables on the relevant kinematical variables in the
center of mass and in the laboratory system, with particular attention to the
effect of the mass induced terms.
