Fe3O4/poly (e-caprolactone)-polyurethane (PCLU) shape memory nanocomposites were prepared by an in situ polymerization method. The thermal properties, magnetic properties, and shape memory properties of the nanocomposites were investigated systematically. The results showed that the Fe3O4 nanoparticles were homogeneously dispersed in the PCLU matrix, which ensured good shape memory properties of nanocomposites in both hot water and an alternating magnetic field (f = 45 kHz, H = 29.7 kA m-1/36.7 kA m-1). The nanocomposites started to recover near 40 degrees C, which is slightly higher than body temperature. Thus, they would not change their deformed shape during the implanting process into the human body. Considering potential clinical applications, 45 degrees C was chosen as shape recovery temperature which is slightly higher than 37 degrees C, and the nanocomposites had high shape recovery rate at this temperature. With increasing content of Fe3O4 nanoparticles, the shape memory properties of the nanocomposites in an alternating magnetic field increased and the best recovery rate reached 97%, which proves that this kind of nanocomposites might be used as potential magnetic sensitive shape memory materials for biomedical applications. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2012