Measurement of Mw from LEP2

In 1997 each LEP experiment collected approximately 55 inv. pb of data at a center-of-mass energy of 183 GeV. These data yield a sample of candidate e+e- -> WW events from which the mass of the W boson, Mw, is measured. The LEP combined result, including data taken at roots = 161 and 172 GeV and assuming the Standard Model relation between the W decay width and mass, is Mw = 80.35 +/- 0.07 (exp) +/- 0.04 (CR) +/- 0.03 (E_beam) GeV, where the errors correspond to experimental, colour-reconnection/Bose-Einstein, and LEP beam energy uncertainties respectively.