  Gravitational lensing and stellar dynamics provide two complementary, nearly
orthogonal, constraints on the mass distribution of early-type lens galaxies.
This allows the luminous and dark-matter distribution in higher-redshift
(z>0.1) galaxies to be studied beyond the limitations of each individual
method. Two surveys have been initiated to compile a large sample of early-type
galaxies suitable to lensing and dynamical studies: (1) The Lenses Structure &
Dynamics (LSD) Survey and (2) the Sloan Lens ACS (SLACS) Survey. Using
spherically symmetric mass models, I illustrated how lensing and dynamical
constraints can be used to measure the ``effective'' density slope (gamma') of
galaxies inside their Einstein radii and estimate the typical error on this
determination. The main results from the LSD survey thus far are: (i) Massive
(typically >L_*) early-type galaxies at z=0.5-1 contain a significant fraction
f_CDM=0.4-0.7 of dark matter inside their Einstein radii. [The null-hypothesis,
f_CDM=0, is excluded at the >99% in all analyzed systems.] (ii) The inner CDM
density slope is gamma_CDM=1.3^{+0.2}_{-0.3} (68% CL). (iii) The total density
slope gamma' = 1.9 +- 0.1 (with 0.3 rms scatter in the sample). The intrinsic
scatter of 15% in gamma' is consistent with local dynamical studies and can
lead to a 30% rms scatter in inferred values of H_0 from lens time-delays, when
purely isothermal mass models are assumed. Hence, the common practice to assume
that lens galaxies are perfectly isothermal should be abandoned, especially in
cases where this assumption is critical.
