  We review X-ray constraints on dark matter in giant elliptical galaxies
(10^{12} M_sun <~ M_vir <~ 10^{13} M_sun) obtained using the current generation
of X-ray satellites, beginning with an overview of the physics of the hot
interstellar medium and mass modeling methodology. Dark matter is now firmly
established in many galaxies, with inferred NFW concentration parameters
somewhat larger than the mean theoretical relation. X-ray observations confirm
that the total mass profile (baryons+DM) is close to isothermal (M ~ r), and
new evidence suggests a more general power-law relation for the slope of the
total mass profile that varies with the stellar half-light radius. We also
discuss constraints on the baryon fraction, super-massive black holes, and
axial ratio of the dark matter halo. Finally, we review constraints on
non-thermal gas motions and discuss the accuracy of the hydrostatic equilibrium
approximation in elliptical galaxies.
