The bcc structure of Ca(ND3)5.7 is found to be stable down to He temperatures. The crystal is characterized by frozen-in orientational disorder and also positional disorder of the ND3 molecules. The latter may be explained by a distribution of octahedrally coordinated and tetrahedrally coordinated Ca ions. The relation of occupation numbers with stoichiometry cannot be made quantitatively, however. There are no indications of a significant departure from the geometry of a free ammonia molecule in the solid.