The results of an experimental investigation of the structure of a separated flow on a flat plate in the region of a three-dimensional shock wave - turbulent boundary layer interaction are presented for free-stream Mach number equal to 3 and Reynolds number Re equals 1.8 x 10(superscript 7). The aim of the investigation is to clarify the general principles governing three-dimensional separated flows induced by the intersection of shock waves formed by obstacles on the body surface with the boundary layer, and to supplement the scarce data available up to now. A schematic presentation of the flow pattern is given. The relationship between the characteristic geometric dimensions of the separation zone and the intensity of the incident shock wave is studied. A comparison is made between two- and three-dimensional cases. (Author).