The dominant one-loop radiative corrections to atomic wave functions. those
associated with vacuum polarization in the nuclear Coulomb field, are eval
uated for the 6s-7s parity-nonconserving transition amplitude in Cs-133. Th
ese corrections increase the size of this amplitude by 0.4% and, correspond
ingly, increase the difference between the experimental value of the weak c
harge Q(W)(Cs-133) and the value predicted by the standard model.