  We summarize theoretical explanations of the three $\sigma$ discrepancy
between $\sin^2 \theta_W$ measured by NuTeV and predicted by the Standard Model
global fit. Possible new physics explanations ({\it e.g.} an unmized $Z'$) are
not compelling. The discrepancy would be reduced by a positive momentum
asymmetry $s^-$ in the strange sea; present experimental estimates of $s^-$ are
unreliable or incomplete. Upgrading the NuTeV analysis to NLO would alleviate
concerns that the discrepancy is a QCD effect.
