Precise measurements of the mass and width of the W boson are
sensitive to radiative corrections and can be used to place limits on new
physics beyond the Standard Model and validate the consistency of the model.
In particular, the W boson mass constrains the mass of the, as yet
unobserved, Higgs boson and the width can be used to place limits on the
existence of new particles that couple to the W.  Results are presented from
p anti-p collisions recorded by the CDF and D0 experiments at the Fermilab
Tevatron collider, operating at a centre of mass energy