Abstract : An exploratory experimental investigation has been carried out on the three dimensional flow fields caused by the interaction of oblique shock waves and a planar turbulent boundary layer. The study was performed at a free stream Mach number of 2.95, a Reynolds number per inch of 1.6 million and near adiabatic wall conditions. The interaction was studied on two experimental configurations having different initial boundary layer thicknesses (delta = approx. 0.13 and 0.55 inches). Both surface measurements as well as complete flow field surveys were performed. The main contributions of the present investigation are two experimentally derived flow field models for shock generator angles of 4 deg and 10 deg. Based upon both static pressure and surface flow patterns, as well as heat transfer data, the interaction region can be characterized as quasi-two-dimensional along the shock direction in the region studied. A critical examination of the occurrence of 'ordinary' flow separation and its character, as applied to the present problem, was carried out. It was concluded that McCabe's criterion, as used by the previous investigators, is not a sufficient condition to determine the onset of flow separation.