Inertia-gravity wave generation resulting from the instability of an energetic ocean current is investigated by means of high-resolution numerical simulations. We consider the efficiency of the generation mechanism as a function of current intensity, structure, position relative to lateral and bottom boundaries and atmospheric forcing. We identify preferred regions of wave generation on the evolving instability wave. The structure of the resulting wave field, its dependence on the characteristics of the unstable current and its tendency to radiate away from the source region is also discussed.