  We calculate the kaon B-parameter, B_K, to next-to-leading order in staggered
chiral perturbation theory. We extend the usual power counting to include the
effects of using perturbative (rather than non-perturbative) matching factors.
Taste breaking enters through the O(a^2) terms in the effective action, through
mixing with higher-dimension operators, and through the truncation of matching
factors. These effects cause mixing with several additional operators,
complicating the chiral and continuum extrapolations. We summarize the results
here; all details can be found in hep-lat/0507012.
