Rattle-type Fe₃0₄@SiO₂ hollow mesoporous spheres with different particle sizes, different mesoporous shell thicknesses, and different levels of Fe₃O₄ content are prepared by using carbon spheres as templates. The effects of particle size and concentration of Fe₃0₄@SiO₂ hollow mesoporous spheres on cell uptake and their in vitro cytotoxicity to HeLa cells are evaluated. The spheres exhibit relatively fast cell uptake. Concentrations of up to 150 μg mL^-1 show no cytotoxicity, whereas a concentration of 200 μg mL^-1 shows a small amount of cytotoxicity after 48 h of incubation. Doxorubicin hydrochloride (DOX), an anticancer drug, is loaded into the Fe₃0₄@SiO₂ hollow mesoporous spheres, and the DOX-loaded spheres exhibit a somewhat higher cytotoxicity than free DOX. These results indicate the potential of Fe₃0₄@SiO ₂ hollow mesoporous spheres for drug loading and delivery into cancer cells to induce cell death.