  The parity violating longitudinal asymmetry ${\cal A}$ is calculated for
quasielastic electron scattering. We use a variety of relativistic mean field
models for the response of nuclear matter and $^{12}$C at a momentum transfer
of q=550 MeV/c. Relativistic effects from a reduced nucleon mass, RPA
correlations and vacuum polarization can all change ${\cal A}$ by a relatively
large amount. These large nuclear structure corrections could make it
impossible to extract strange quark matrix elements or radiative corrections to
weak axial currents.
