  We review the motivation and search for supermassive black holes (BHs) in
galaxies. Energetic nuclear activity provides indirect but compelling evidence
for BH engines. Ground-based dynamical searches for central dark objects are
reviewed in Kormendy & Richstone (1995, ARA&A, 33, 581). Here we provide an
update of results from the HST. As of 2001 March, dynamical BH detections are
available for at least 37 galaxies. The demographics of these objects lead to
the following conclusions: (1) BH mass correlates with the luminosity of the
bulge component of the host galaxy. The median BH mass fraction is 0.13% of the
mass of the bulge. (2) BH mass correlates with the mean velocity dispersion of
the bulge inside its effective radius. For the best mass determinations, the
scatter is consistent with the measurement errors. (3) BH mass correlates with
the luminosity of the high-density central component in disk galaxies
independent of whether this is a real bulge (a mini-elliptical, believed to
form via a merger-induced dissipative collapse and starburst) or a
``pseudobulge'' (believed to form by inward transport of disk material). (4) BH
mass does not correlate with the luminosity of galaxy disks. If pure disks
contain BHs, then their masses are much smaller than 0.13% of the mass of the
disk. We conclude that present observations show no dependence of BH mass on
the details of whether BH feeding happens rapidly during a collapse or slowly
via secular evolution of the disk. The above results increasingly support the
hypothesis that the major events that form a bulge or elliptical galaxy and the
main growth phases of its BH -- when it shone like a quasar -- were the same
events.
