\We present a measurement of the W boson mass using data collected by the D
O experiment at the Fermilab Tevatron during 1994-1995. We identify W boson
s by their decays to ev final states where the electron is detected in a fo
rward calorimeter. We extract the W boson mass M-W by fitting the transvers
e mass and transverse electron and neutrino momentum spectra from a sample
of 11 089 W-->e nu decay candidates. We use a sample of 1687 dielectron eve
nts, mostly due to Z-->ee decays, to constrain our model of the detector re
sponse. Using the forward calorimeter data, we measure M-w=80.691+/-0.227 G
eV. Combining the forward calorimeter measurements with our previously publ
ished central calorimeter results, we obtain M-W= 80.482 +/-0.091 GeV.