Crystals with two different habits (e.g. needle-like and plate-like) of ciprofloxacin hydrochloride monohydrate (CPFX) were prepared from aqueous solution by varied methods. These crystals were identified by various means such as scanning electron microscope (SEM),differential scanning calorimetry (DSC), thermogravimetry (TG), and X-ray powder diffraction (XRPD). According to the analysis of crystals by DSC, TG and XRPD, it concludes that CPFX crystals produced in cooling or dilution crystallization experiment should have the same crystal structure. Using the XRPD data, the unit cell parameters were calculated by software TREOR90. Systematic absence and statistics of reflexion indicate that CPFX crystals in this work have a high possibility of being the space group P2(1)/c. The crystal habit transition has been observed in the salting-out crystallization when 0.2 M KCl solution works as precipitant. (c) 2004 Elsevier B.V. All rights reserved.