  The different methods of determination of black holes (BHs) masses are
presented for three classes of BHs observed in the Universe: stellar mass BHs,
intermediate mass BHs (IMBHs) and supermassive BHs (SBHs). The results of these
determinations are briefly reviewed: stellar mass BHs are found in the range of
about 3 to about 20 solar masses, IMBHs in the range of a few hundreds to a few
tens of thousands solar masses (the determinations are much less precise for
these objects) and SBHs in the range of about 3x10^5 to about 6x10^10 solar
masses.
