In this study, we describe a simple approach to preparing single-crystal Fe3O4 nanorods in the presence of poly(vinylpyrrolidone) (PVP). The morphologies of the nanorods are characterized by transmission electron microscopy (TEM), which indicates that these nanorods are formed by nucleation and growth process in situ in aqueous solution. A superconducting quantum interference device (SQUID) magnetometer characteristic of the as-synthesized Fe3O4 nanorods shows superparamagnetic, properties. (C) 2004 Elsevier Inc. All rights reserved.