  We report on Keck optical BVRI images and spectroscopy of the companion of
the binary millisecond pulsar PSR J0218+4232. A faint bluish (V=24.2, B-V=0.25)
counterpart is observed at the pulsar location. Spectra of this counterpart
reveal Balmer lines which confirm that the companion is a Helium-core white
dwarf. We find that the white dwarf has a temperature of Teff=8060+-150 K.
Unfortunately, the spectra are of insufficient quality to put a strong
constraint on the surface gravity, although the best fit is for low log g and
hence low mass (~0.2 Msun), as expected. We compare predicted white dwarf
cooling ages with the characteristic age of the pulsar and find similar values
for white dwarf masses of 0.19 to 0.3 Msun. These masses would imply a distance
of 2.5 to 4 kpc to the system. The spectroscopic observations also enable us to
estimate the mass ratio between the white dwarf and the pulsar. We find
q=7.5+-2.4, which is consistent with the current knowledge of white dwarf
companions to millisecond pulsars.
