Details of dislocation structure have been determined for a variety of NaCl whiskers and microcrystals grown from porous substrates moistened with supersaturated aqueous solution. Some of the smaller needle‐like crystals have the single dislocation with an axial screw component usually assumed for whiskers. Larger whiskers and platelets often have much more complicated dislocation structures and may have higher dislocation densities than normal bulk crystals. Strengths were compared with dislocation structures and it was found that the nearly theoretical strengths observed in some of these whiskers are not due to merely a size effect but are directly related to the dislocation structure. Even crystals with high dislocation densities exhibited high strength in bending provided that all of the dislocations were so arrayed that they were not influenced by the applied stress. Regular dislocation arrays often occur naturally with this growth mechanism. However, irregular dislocation structures often associated with growth irregularities invariably resulted in low strength. Techniques for application of x‐ray diffraction microscopy to determination of the dislocation structure of microcrystals are described.