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.