This paper describes a flexible stereo verification system, STEREOSYS, and its application to the analysis of high resolution aerial photography. Stereo verification refers to the verification of hypotheses about a scene by stereo analysis of the scene. Unlike stereo interpretation, stereo verification requires only coarse indications of three-dimensional structure. In the case of aerial photography, this means coarse indications of the heights of objects above their surroundings. This requirement, together with requirements for robustness and for dense height measurements, shapes the decision about the stereo system to use. This paper discusses these design issues and describes an implementation.