The purpose of these experiments conducted in the shock tube was to obtain qualitative information concerning the effect of various types and degrees of surface roughness on the diffraction of a shock wave about a two-dimensional model. A series of shadowgraphs was taken of the various blocks in the shock tube with incident over-pressure of 6 and 9 psi. Qualitative analysis of the data indicates that surface roughness reduces the velocity of the shock across the top near the rough surface and tends to hinder the developmemt of the front top vortex appreciably, but does not affect the development of the rear vortex to as great an extent.