Following a short account of the history of the idea of black holes, we
present a review of the current status of the search for observational evidence
of their existence aimed at an audience of relativists rather than astronomers
or astrophysicists. We focus on two different regimes: that of stellar-mass
black holes and that of black holes with the masses of galactic nuclei.Comment: 23 pages, 3 figures, TeX forma
