Values of interplanar angles useful in distinguishing the [100] from the [110] direction in CaMoO4 are given to facilitate orientation by analysis of back-reflection Laue patterns. The distinction between the [001] and [ 00 1 ¯ ] directions in the scheelite structure is discussed and examples of physical properties dependent upon this distinction are given. The [001] direction is denned in terms of the crystal structure and a procedure for identifying [001] using Laue patterns is described. The same distinction applies to certain nonpolar directions of all crystals belonging to the following nonenantio morphous point groups: 1 ¯ , m, 2/m, mmm, 3 ¯ , 3m, 3 ¯ m, 4 ¯ , 4/m, 4/mmm, 6 ¯ , 6/m, 6/mmm, m3 and m3m.