  I present a measurement of the W boson mass (M_W) and width (G_W) using 200
and 350 pb-1 of CDF Run II data respectively. The measurements, performed in
both the electron and muon decay channels, rely on a fit to the W transverse
mass distribution. We measure M_W = 80413 +/- 48 MeV and G_W = 2032 +/- 71 MeV
which represent the world's single most precise measurements to date.
