Redetermination of the structure of DL-norleucine (2-aminohexanoic acid), C6H13NO2, has given more accurate geometrical information than the early work of Mathieson [Acta Cryst. (1953), 6, 399-403]. Synchrotron radiation Laue diffraction patterns recorded over a range of temperatures have shown (a) the presence of streaks, indicating disorder in the stacking of layers within the crystal at room temperature, (b) complete or almost complete disappearance of these streaks when the crystal is heated to ca 373 K, indicating annealing of the crystal, and (c) loss of single crystal characteristics above 390 K so that it was not possible to record diffraction data for the high-temperature form proposed by Mathieson.