Disclosed is a crystalline Form D of topotecan hydrochloride characterized by a powder X-ray diffraction pattern having peaks at 5.9, 13.9, 22.6, 23.2 and 26.5 o20 (+0.2o). Further disclosed is a process for preparing the topotecan hydrochloride as described above comprising: (a) dissolving topotecan hydrochloride in a first solvent system (b) adjusting the pH of the resulting mixture of step (a) to below 1.2 c) adding a volume of low polar solvent into the mixture of step (b) to form a second solvent system, wherein the first solvent system is more polar than the second solvent system and (d) crystallizing the topotecan hydrochloride Form D from the second solvent system.
