During the past 15 years, the importance of stray light control and its evaluation as an integral part of the design process for imaging systems has emerged. There has been substantial progress in the development of both analytical tools and experimental facilities. The problem has become easier and more difficult depending on the scenario. Some scenarios such as detecting point objects within a small field of view have made the problem easier as the background stray light is proportional to the field of view. Extended objects and large fields of view make the problem more difficult as does near field thermal sources. It is for these reasons that a review is in order-to assess our present technology and suggest how we might develop that technology.