This paper presents some results of a study on the direct scattering problem. However, due to the intimate relationship between direct and inverse scattering, the results also have relevance for inverse scattering. In fact, the motivation for the study came from a need to test some of the assumptions we make in diffraction tomography experiments, i. e. , most importantly, to verify that we can indeed faithfully measure in the laboratory the data predicted by our theoretical model. To achieve this aim, the scattering of plane ultrasound waves by penetrable circular cylinders was investigated both theoretically and experimentally. This particular geometry was chosen since it is possible to compute an exact solution for the direct scattering problem.