  The electroweak theory has been tested to high precision, with measurements
probing its predictions at the loop level. The current generation of particle
accelerators will produce enough W and Z bosons through hadron collisions to
significantly improve the accuracy of these measurements. I review the issues
related to such production, with particular emphasis on associated
uncertainties on the W boson mass, which has now been measured more precisely
at the Tevatron than at the Large Electron Positron collider.
