  We calculate stellar masses for massive luminous galaxies at redshift 0.2-0.7
using the first two years of data from the Baryon Oscillation Spectroscopic
Survey (BOSS). Stellar masses are obtained by fitting model spectral energy
distributions to u,g,r,i,z magnitudes, and simulations with mock galaxies are
used to understand how well the templates recover the stellar mass. Accurate
BOSS spectroscopic redshifts are used to constrain the fits. We find that the
distribution of stellar masses in BOSS is narrow (Delta log M~0.5 dex) and
peaks at about logM ~ 11.3 (for a Kroupa initial stellar mass function), and
that the mass sampling is uniform over the redshift range 0.2 to 0.6, in
agreement with the intended BOSS target selection. The galaxy masses probed by
BOSS extend over ~10^{12} M, providing unprecedented measurements of the
high-mass end of the galaxy mass function. We find that the galaxy number
density above ~ 2.5 10^{11} M agrees with previous determinations. We perform a
comparison with semi-analytic galaxy formation models tailored to the BOSS
target selection and volume, in order to contain incompleteness. The abundance
of massive galaxies in the models compare fairly well with the BOSS data, but
the models lack galaxies at the massive end. Moreover, no evolution with
redshift is detected from ~0.6 to 0.4 in the data, whereas the abundance of
massive galaxies in the models increases to redshift zero. Additionally, BOSS
data display colour-magnitude (mass) relations similar to those found in the
local Universe, where the most massive galaxies are the reddest. On the other
hand, the model colours do not display a dependence on stellar mass, span a
narrower range and are typically bluer than the observations. We argue that the
lack of a colour-mass relation for massive galaxies in the models is mostly due
to metallicity, which is too low in the models.
