  Radial velocity studies of X-ray binaries provide the most solid evidence for
the existence of stellar-mass black holes. We currently have 20 confirmed
cases, with dynamical masses in excess of 3 Msun. Accurate masses have been
obtained for a subset of systems which gives us a hint at the mass spectrum of
the black hole population. This review summarizes the history of black hole
discoveries and presents the latest results in the field.
