Recent clinical and experimental works in the area of bioelectromagnetics are reviewed and considered from a physical viewpoint. An equation relating the intrinsic (or 'rest') energy of a charged particle with its energy of interaction in an externally applied magnetic field is proposed. This equation is intended to represent an initial basic physical interaction which may be part of a more complex biological mechanism that may explain the potential effects of externally applied magnetic fields. Speculations are presented on the potential use of magnetic fields for the non-invasive treatment of such diverse conditions such as cancer, AIDS and neurological disorders.