  We review a little-known treatment of the relativistic two-body bound-state
problem - that provided by Two-Body Dirac Equations obtained from constraint
dynamics. We describe some of its more important results, its relation to older
formulations and to quantum field theory. We list a number of features crucial
for the success of such a formulation, many of which are missing from other
methods; we show how the treatment provided by Two-Body Dirac Equations
encompasses each of them.
