A new technique is described which provides for the study of x‐ray diffraction from a small selected region in the interior of a body. The method is of particular value for the measurement of interior elastic strain and will permit the complete evaluation of a triaxial state of stress. The collimation is appropriate for studies of either single crystals or polycrystalline material. Evaluations on single crystals of LiF with Mo K&agr;1demonstrate that a conventional line x‐ray source provides useful diffracted power from a crystal volume of less than 10−4cm3located at a depth below the surface exceeding 0.3 cm. A strain reproducibility of better than 2×10−5was attained in measurements at several depths in an unstrained crystal, and elastic strain evaluations were made through the thickness of a single crystal beam loaded in four‐point bending.