The recent interest in hypersonic atmospheric flight is bringing new attention to shock boundary-layer interaction problems. Engine inlets, fins, and surface contouring among others can lead to unswept and swept laminar and turbulent interactions. Many questions still remain with respect to the underlying flow physics which provides motivation for both experimental and numerical research in the area. In this paper results from preliminary simulations of oblique shock waves impinging on a flat plate are presented. The numerical approach is first validated for a laminar interaction. Both the Reynolds number and the shock incidence angle are then increased until the flow becomes unsteady. Interestingly, the three-dimensional flow becomes unsteady at a lower Reynolds number than the two-dimensional flow. Velocity fluctuations from a compressible channel flow simulation are then used to “seed” a turbulent boundary layer upstream of the interaction. Compared to the laminar interaction for the same Reynolds number, the separated flow region is much reduced.