Nanoscale magnetic materials may have several potential applications in the biomedical area. An example thereof are superparamagnetic iron oxide nanoparticles, which, due to large own surface and ability to interact with various tissues, are used to detect and analyze biological molecules, in targeted drug delivery, for contrast enhancement in magnetic resonance imaging studies and, last but not least, in therapeutic hyperthermia. When used for medical purposes, magnetic nanoparticles often require coating with a biocompatible polymer, preventing its detection by the immune system, encapsulation by plasma proteins and excretion, while at the same time facilitating binding with organic complexes, which subsequently may accumulate in definite pathological foci. Widespread use of magnetic nanoparticles is associated with heat generation. When placed within neoplastic tissue and exposed to alternating external magnetic field, magnetic nanoparticles generate a local heating effect. Local elevation of tissue temperature has a potent cytostatic effect mediated by denaturation of proteins and destruction of intracellular structures, leading to reduction of tumor mass. Temperature obtained within the tumor depends on properties of magnetic nanoparticles used and parameters of external magnetic field applied, i.e. amplitude and frequency of field oscillations. This physical phenomenon results in direct destruction of tumor cells. Furthermore, local elevation of body temperature contributes to enhanced effectiveness of chemo- and radiotherapy. The paper is a review of current applications of superparamagnetic metal nanoparticles in oncology.