  The orbital motion of inspiralling and coalescing black hole binaries can be
investigated using a variety of approximation schemes and numerical methods
within general relativity: post-Newtonian expansions, black hole perturbation
theory, numerical relativity, and the effective-one-body formalism. We review
two recent comparisons of the predictions from these various techniques. Both
comparisons rely on the calculation of a coordinate invariant relation, in the
case of non-spinning binary black holes on quasi-circular orbits. All methods
are shown to agree very well in their common domain of validity.
