  In this paper we derive a Gauss-Bonnet formula for the renormalized area of
Graham-Witten minimal hypersurfaces of 5-dimensional Poincar\'e-Einstein
spaces. The formula we derive expresses the renormalized area in terms of
integrals of pointwise scalar Riemannian invariants. We also prove a result
which gives a characterization of minimal hypersurfaces with $L^2$ second
fundamental form in terms of conformal geometry at infinity.
