Relics of Nuclear Activity: do all galaxies have massive black holes?

The distribution of black hole masses in galaxies is constrained by photometric and kinematic studies of individual galaxies, and by the properties of the quasar population. I review our understanding of these topics, present new results of adiabatic black hole growth models for HST photometry of elliptical galaxies with brightness profiles of the `core' type, and discuss the implications of ground-based stellar kinematical data. It is not yet possible to uniquely determine the black hole mass distribution, but the available evidence is not inconsistent with a picture in which: (i) a majority of galaxies has black holes; (ii) there is a correlation (with large scatter) between black holes mass M_BH and spheroid luminosity L_sph, approximately of the form M_BH = 10^{-2} L_sph (in solar B-band units); and (iii) the black holes formed in a quasar phase through mass accretion with an efficiency of approximately 0.05.