  We have witnessed a dramatic increase over the last five years in results on
distant galaxies, in large part because of the high resolution imaging
capability of HST, and the multiobject spectroscopic capability of the Keck
telescopes. Our program to obtain wide-field, multi-color WFPC2 mosaics with
HST of intermediate redshift clusters, and spectroscopic membership and high
S/N spectroscopy with LRIS on Keck, has provided new insights into the nature
of elliptical and S0 galaxies in the cluster environment over a wide range of
densities. In particular, most ellipticals, and a significant fraction of the
S0 population, have large luminosity-weighted ages, suggesting that their
stellar populations were formed at redshifts beyond z~2, though the existence
of substantial numbers of major mergers in MS 1054-03 at z=0.83 suggests that
final assembly of such galaxies may not have occurred until much later for a
significant fraction of early-type galaxies.
