The present invention relates to crystalline anhydrate polymorphs of the dihydrogenphosphate salt of (2R)4-oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-.alpha.]p- yrazin-7(8H) yl]-1-(2,4,5-trifluorophenyl)butan-2-amine as well as a process for their preparation, pharmaceutical compositions containing these novel forms, and methods of use of the novel forms and pharmaceutical compositions for the treatment of diabetes, obesity, and high blood pressure. The invention also concerns novel crystalline solvates of the dihydrogenphosphate salt of (2R)-4-oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]tria-zolo [4,3-.alpha.]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine as well as a crystalline desolvated polymorph and their use for the preparation of the anhydrate polymorphs of the present invention.