  The dominant one-loop radiative corrections to atomic wave functions, those
associated with vacuum polarization in the nuclear Coulomb field, are evaluated
for the 6s-7s parity-nonconserving (PNC) transition amplitude in 133Cs. These
corrections increase the size of the PNC amplitude by 0.4% and,
correspondingly, increase the difference between the experimental value of the
weak charge Q_W(133Cs) and the value predicted by the standard model.
