  We discuss the method, and potential systematic effects therein, used for
measuring the mass of stellar-mass black holes in X-ray binaries. We restrict
our discussion to the method that relies on the validity of Kepler's laws; we
refer to this method as the dynamical method. We briefly discuss the
implications of the mass distribution of stellar-mass black holes and provide
an outlook for future measurements. Further, we investigate the evidence for
the existence of intermediate-mass black holes i.e. black holes with masses
above 100 Msun, the limit to the black hole mass that can be produced by
stellar evolution in the current Universe.
