A new method for the preparation of tetranitroglycoluril (TNGU, Sorguyl) is described, in which imidazo-[4,5-d]-imidazoles are nitrated with the elimination of N2O to generate TNGU. This method of TNGU synthesis results in material that is less sensitive than material produced with alternative routes. Additionally, a new spherical morphology of TNGU is disclosed. This morphology exhibits an even higher resistance to external insult even than material synthesized with the new method.