Hollow CoFe2O4 spheres consisted of CoFe2O4 nanoparticles were synthesized by a facile solvothermal treatment of an ethylene glycol solution of FeCl3 center dot 6H(2)O, CoCl2 center dot 6H(2)O, and NaAc at 200 degrees C in the presence of polyethylene glycol and oleic acid. The products were characterized by powder X-ray diffraction, transmission electron microscopy, selected area electron diffraction, high-resolution transmission microscopy, scanning electron microscopy. The magnetic properties were evaluated using a vibrating sample magnetometer. The probable mechanism of the formation of Hollow CoFe2O4 spheres was discussed.