Stereoradiographs have been used on occasion for three-dimensional reconstruction and measurement of objects in radiology and radiotherapy. The lack of a good stereoradiographic technique has limited the uses of steroradiographic exposures. In this paper, the principle of the double-image is outlined and a method of applying this principle to stereoradiographic exposures is developed. A computer program has been developed from geometrical considerations to analyze the stereobronchogram and to calculate the dimensions of the objects in question. The applications of this technique are discussed and its use in evaluating lung casts is described.