We present a measurement of the W boson mass using 200 pb-1
of data collected in p anti-p collisions at s**(1/2) = 1.96 TeV by the
CDF II detector at Run II of the Fermilab Tevatron. With a sample of
63964 W --> e nu candidates and 51128 W --> mu nu candidates,
we measure M_W ÿ80413 +/- 34_stat +/- 34_syst ø0413 +/- 48) MeV/c2.
This is the most precise single measurement of the W boson mass to date.