  We present recent developments in the diagnostic study of heavy gauge bosons
at future colliders with the emphasis on the determination of gauge couplings
of $Z'$ to quarks and leptons. Proposed diagnostic probes at future hadron
colliders are discussed. The study of statistical uncertainties expected for
the above probes at the LHC and $M_{Z'}\simeq 1$ TeV shows that three out of
four normalized couplings can be determined, thus allowing for a distinction
between models. The complementary nature of the probes at future $e^+e^-$
colliders is also discussed.
