  For the first time, charge symmetry breaking terms in parton distribution
functions have been included in a global fit to high energy data. We review the
results obtained for both valence and sea quark charge symmetry violation, and
we compare these results with the most stringent experimental upper limits on
charge symmetry violation for parton distribution functions, and with
theoretical estimates of charge symmetry violation. The limits allowed in the
global fit would tolerate a rather large violation of charge symmetry. We
discuss the implications of this for the extraction of the Weinberg angle in
neutrino DIS by the NuTeV collaboration.
