The atomic structure of the σ= 5, (310)[001] grain boundary in NiAl has been determined by a synergistic approach using high-resolution electron microscopy and atomistic structure calculations. These calculations employ N-body empirical potentials which were developed for the NiAl phase. A minimum-energy structure was determined which produced calculated images which matched experimental images of the boundary. The change in interfacial energy due to various defects at the grain boundary was also examined. This is the, first concurrent application of experimental and theoretical structure determinations to a grain boundary in an intermetallic compound.