Unique information about the hardness properties of crystalline materials can be obtained from studying the dislocation mechanisms involved in microindentation testing. The dislocation description provides information in addition to the knowledge of indentation processes gained from earlier continuum mechanics analyses and from models of the orientation dependence of hardness based on the geometrical arrangement of slip systems. For example, (1) mapping of the residual dislocation distributions within microindentation plastic zones can be used to characterize the deformation field and (2) specification of the dislocation interactions that occur among the crystal deformation systems is useful in evaluating the extent to which the hardness is affected by work hardening and cracking mechanisms. An interesting application of this information is to microindentation hardness testing of explosive crystals.