Crystalline adinazolam methanesulfonate which is essentially non-hygroscopic is a novel product. It can be prepared by mixing adinazolam free base and methanesulfonic acid in analkanol/alkyl acetate mixture heating the mixture to remove alkanol and any water and separating the precipitate after cooling.

4210 Crystalline non-hygroscopic adinazolam methanesulfonate per se preparable from xylene or preferably from a C1 to C2-alkanol/C4 to C6alkyl acetate liquid mixture aids processability of adinazolam methanesulfonate in pharmaceutical production plants.

Crystalline non-hygroscopic adinazolam methanesulfonate per se preparable from xylene or preferably from a C.sub.1 to C.sub.2 -alkanol/C.sub.4 to C.sub.6 -alkyl acetate liquid mixture aids processability of adinazolam methanesulfonate in pharmaceutical production plants.

Crystalline adinazolam methanesulphonate (I) which is essentially non-hygroscopic is new. Adinazolam (8-diloro-1-(dimethylamino)methyl -6-phenyl-4H-s-triazolo(43-a)(1- 4) benzodiazepine) and its methanesulphonate are described and claimed in US 4250094.