  Supermassive black holes appear to be uniquely associated with galactic
bulges. The mean ratio of black hole mass to bulge mass was until recently very
uncertain, with ground based, stellar kinematical data giving a value roughly
an order of magnitude larger than other techniques. The discrepancy was
resolved with the discovery of the M-sigma relation, which simultaneously
established a tight corrrelation between black hole mass and bulge velocity
dispersion, and confirmed that the stellar kinematical mass estimates were
systematically too large due to failure to resolve the black hole's sphere of
influence. There is now excellent agreement between the various techniques for
estimating the mean black hole mass, including dynamical mass estimation in
quiescent galaxies; reverberation mapping in active galaxies and quasars; and
computation of the mean density of compact objects based on integrated quasar
light. Implications of the M-sigma relation for the formation of black holes
are discussed.
