Garnets of diverse compositions, including natural birefringent specimens and certain synthetic garnets, have been found to be noncubic. These include anisotropic grandites, for which successful crystal-structure refinements have been carried out in space groups Fddd and IĪ; an intermediate pyralspite-grandite with space group I4₁/acd; and synthetic Mg-silicate and Mn-silicate garnets, both with space group J4₁/a. Reconnaissance work on pyralspites has revealed that some of these, too, are optically anisotropic, but the space groups are as yet unde- termined. In all cases for which crystal-structure refinements have been done, ordering of cations has been identified as the cause of anisotropy. Symmetry analysis, based on Landau theory and the theory of induced representations, has been used determine which space groups and ordering schemes can result from transformation from Ia3d (the space group of cubic garnets). Three irreducible representations of Ia3 d yield phase transitions driven by a single order parameter and also give the space groups observed for noncubic garnets: T_2g, E_g, and T_1g, These describe three ordering routes: the T_2g route leads to possible space groups R 3 c, Fdd, I2/c, and /Ī; the E_g route leads to possible space groups I4₁/acd and Ibca; and the T_tg route leads to possible space groups R 3, I4₁/a, I2/c, and IĪ. Although ordering could result during primary crystal growth, the weight of evidence seems to favor phase transformation as the cause of ordering in the birefringent silicate garnets investigated thus far. In particular, the ordering patterns observed are precisely the ones predicted by the theory on the assumption of a phase transformation; and transformation twins, also predicted, are observed in at least one of the noncubic garnets.