Carbon nanotubes embedded with nanosized magnetic materials are novel and interesting materials which could provide a wide range of possible applications with an emphasis in biomedicine. A facile and efficient method was developed to fill multi-walled carbon nanotubes (MWCNTs) with Fe3O4 nanoparticles. X-ray diffraction, Fourier transform infrared spectrometry, thermal gravimetry, transmission electron microscopy, and vibrating sample magnetometry were used to characterize the physical and magnetic properties of the hybrid obtained. The results confirmed that MWCNTs and Fe3O4 NPs coexisted in the hybrid.The magnetic measurement shows that Fe3O4-filled pretreated MWCNTs exhibit superparamagnetism. Results showed that the Fe3O4-filled pretreated MWCNTs exhibited superparamagnetism at room temperature and possessed a higher saturation magnetization (Ms) (around 33.8 emu/g) than that of the unfilled MWCNTs (around 0.35 emu/g). The product displays potential applications in biomedicine and engineering. (C) 2013 Elsevier B.V. All rights reserved.