  Strong gravitational lensing and stellar dynamics provide two complementary
and orthogonal constraints on the density profiles of galaxies. Based on
spherically symmetric, scale-free, mass models, it is shown that the
combination of both techniques is powerful in breaking the mass-sheet and
mass-anisotropy degeneracies. Second, observational results are presented from
the Lenses Structure & Dynamics (LSD) Survey and the Sloan Lens ACS (SLACS)
Survey collaborations to illustrate this new methodology in constraining the
dark and stellar density profiles, and mass structure, of early-type galaxies
to redshifts of unity.
