Results are presented from the analysis of ROSAT HRI and PSPC observations of the CNOC subsample of the EMSS high redshift galaxy clusters .
X-ray surface brightness profiles of 14 clusters with 0.17 < z < 0.55 are constructed and fit to isothermal \beta models .
Where possible , we use both the HRI and PSPC data to constrain the fit .
Under the assumptions of isothermality , hydrostatic equilibrium , and spherical symmetry , we derive total X-ray masses within a range of radii from 141 to 526 h ^ { -1 } _ { 100 } kpc .
These masses are compared with both the dynamical masses obtained from galaxy velocities and the projected masses from published gravitational lensing studies .
We find no systematic bias between X-ray and dynamical methods across the sample , with an average M _ { Dyn } / M _ { X } = 1.04 \pm 0.07 , although individual clusters exhibit mass discrepancies up to a factor of 2 .
We estimate that the systematic effects due to cooling flows , non-equilibrium systems and temperature gradients affect the average mass ratio by no more than 15 - 20 \% .
Weak gravitational lensing masses appear to be systematically higher than X-ray results by factors of \sim 50 \% , while strong lensing estimates show larger discrepancies ( factors of \sim 2.5 ) .
However , these comparisons are complicated by the need to extrapolate the X-ray data to larger or smaller radii .
X-ray derived cluster gas masses are calculated , from which we obtain a cluster baryon fraction of \sim 5 \%h ^ { -3 / 2 } _ { 100 } , yielding \Omega _ { 0 } \sim 0.3 h ^ { -1 / 2 } _ { 100 } .