Rattle-type Fe ₃O ₄@SiO ₂ hollow mesoporous spheres with large cavities have been successfully prepared by using the colloidal carbon spheres as the templates. The spheres are well monodisperse and nearly uniform in dimension with particle size of ca. 900 nm. The thickness of the mesoporous silica shell is about 100 nm, and only one Fe ₃O ₄ particle of ca. 100 nm in diameter is encapsulated in each hollow mesoporous silica sphere. The magnetic measurement indicated that the Fe ₃O ₄@SiO ₂ hollow mesoporous spheres exhibited ferromagnetic behavior with the magnetization saturation of 1.6 emu/g. Using aspirin as a model drug, the Fe ₃O ₄@SiO ₂ hollow mesoporous spheres showed high drug loading capacity and sustained release property. Therefore, this kind of magnetic hollow mesoporous spheres provides a very promising candidate for application in a targeted drug delivery system.