The vortex produced by a weak shock passing over a 5° vertical wedge has been studied experimentally and theoretically. The theory applies to any vortex in isentropic flow which has a certain rotational symmetry, and which expands uniformly in time (pseudo‐stationary flow), without consideration of how the vortex was formed. By fitting essentially one parameter of the theory to the interferometrically observed density, good agreement is obtained over the region of the vortex, except at the very center. The rate of growth of the vortex as a function of free‐stream Mach number has been found in agreement with that predicted by [N. Rott (private communication)] on the basis of another theory. The photographs show a well‐developed spiral slip stream winding off the corner which contains small secondary eddies whose average angular spacing, measured from the vortex center, appears to be roughly independent of shock strength and time.