Resuits are presented from HNF and RDX ciystallisation experiments and the effect thereof on the properties of these materials. Control of the crystallisation process for HNF will improve the particle shape, the stability and the processability. Other parameters, like sensitivity, are much better reproducible and the control over the particle size will be unproved. For RDX especially the processability and the sensitivity to shock are iinproved when the particles are spherodised or treated in another•way. Photographs of the crystals are presented as well as the properties of the various batches.