The invention relates to the preparation and characterization of novel forms of (1-hydroxy-2-imidazol-1-yl-1-phosphono-ethyl) phosphonic acid. The invention also relates to the use of the novel forms of (1-hydroxy-2-imidazol-1-yl-1-phosphono-ethyl) phosphonic acid in pharmaceutical compositions in drug delivery systems for humans. The invention further relates to the use of the novel forms of (1-hydroxy-2-imidazol-1-yl-1-phosphono-ethyl) phosphonic acid or the pharmaceutical compositions thereof to treat and/or prevent a disease state associated with osteoporosis, tumor induced hypercalcemia (TIH), cancer-induced bone metastasis, Paget's disease or for adjuvant or neoadjuvant therapies.