  I review the status of lattice QCD calculations of the hadronic contributions
to the muon's anomalous magnetic moment, focussing on the hadronic vacuum
polarisation contribution which dominates the uncertainty of the Standard Model
prediction.This quantity exhibits a tension between recent lattice QCD results
and the traditional data-driven dispersive method. I discuss the implications
for the running of the electromagnetic coupling and the consistency of global
fits using electroweak precision data.
