  We investigate the stellar masses of the class of star-forming objects known
as Luminous Compact Blue Galaxies (LCBGs) by studying a sample of galaxies in
the distant cluster MS$~$0451.6-0305 at $z\approx0.54$ with ground-based
multicolor imaging and spectroscopy. For a sample of 16
spectroscopically-confirmed cluster LCBGs (colour $B-V < 0.5$, surface
brightness $\mu_B < 21$ mag arcsec$^{-2}$, and magnitude $M_B < -18.5$), we
measure stellar masses by fitting spectral energy distribution (SED) models to
multiband photometry, and compare with dynamical masses (determined from
velocity dispersion between 10 $<$ $\sigma_v (\rm km~ s^{-1})$ $<$ 80), we
previously obtained from their emission-line spectra. We compare two different
stellar population models that measure stellar mass in star-bursting galaxies,
indicating correlations between the stellar age, extinction, and stellar mass
derived from the two different SED models. The stellar masses of cluster LCBGs
are distributed similarly to those of field LCBGs, but the cluster LCBGs show
lower dynamical-to-stellar mass ratios ($\rm M_{dyn}/M_{\ast} = 2.6$) than
their field LCBG counterparts ($\rm M_{dyn}/M_{\ast}=4.8$), echoing trends
noted previously in low-redshift dwarf elliptical galaxies. Within this limited
sample, the specific star formation rate declines steeply with increasing mass,
suggesting that these cluster LCBGs have undergone vigorous star formation.
