The present invention relates to novel polymorphs of (2E)-1-hydroxy-2-methylpent-2-enyl-pyrophosphonate disodium (CHDMAPP-Na2), to the process for preparing them and to the pharmaceutical compositions containing them.Cette invention concerne de nouveaux polymorphes du (2E)-1-hydroxy- 2-méthylpent-2-ényl-pyrophosphonate disodique (CHDMAPP-Na2), leurs procédés de préparation et des compositions pharmaceutiques les contenant.