  A review is given of latest results on tests of the flavour independence of
strong interactions. Heavy quark mass effects are evident in the data and are
now taken into account at next-to-leading order in QCD perturbation theory. The
strong-coupling ratios alpha_s^b/alpha_s^uds and alpha_s^c/alpha_s^uds are
found to be consistent with unity. Determinations of the b-quark mass m_b(M_Z)
are discussed.
