Measurements have been made of the distribution of exposure dose in the neighborhood of a plane boundary separating two media of very different density, steel-wool and steel. A point-isotropic Co60 source was located in the vicinity of the boundary. Control measurements were performed in a homogeneous medium of steel-wool. In this way the effect on gamma-ray propagation of an abrupt density change was established. The main result was a progressive decrease of exposure dose near the density-interface compared with the homogeneous medium situation, as the source-detector distance was increased. There is good agreement between the experimental results and corresponding Monte Carlo calculations.