  The evolution of AGN in groups and clusters provides important information
about how their black holes grow, the extent to which galaxies and black holes
coevolve in dense environments, and has implications for feedback in the local
universe and at the epoch of cluster assembly. I describe new observations and
analysis that demonstrates that the AGN fraction in clusters increases by a
factor of eight from the local universe to z~1 and that this evolution is
consistent with the evolution of star-forming galaxies in clusters. The cluster
AGN fraction remains approximately an order of magnitude below the field AGN
fraction over this entire range, while a preliminary analysis of groups
indicates that they too undergo substantial evolution.
