Chemical etching technique has been used for the first time to reveal dislocation structure of the cleavage plane of L-arginine hydrofluoride monohydrate (LAHF). Selective behaviour of the etchants for revealing macrosteps and cooperating spirals has been demonstrated. Presence of growth spirals on (1 0 0) face indicates that growth of this face is governed by screw dislocation mechanism. Microhardness measurement reveals that LAHF is harder than LAP. (c) 2004 Elsevier B.V. All rights reserved.